Foot & Ankle Bone Tumors

8/2/2019 Foot & Ankle Bone Tumors

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AneurysmalBoneCystIntroduction and Definition:

This lesion is not a true neoplasm, but rather is thought to be a reactive lesion that may be caused by a local arteriovenous

malformation or vascular injury. The true cause is unknown. There is a definite relationship to local trauma in some cases, and

other cases are associated with another tumor such as osteoblastoma, chondroblastoma, fibrous dysplasia, or other. A large

proportion of these lesion appear to arise de novo without any definite traumatic or neoplastic cause.

Incidence and Demographics:

ABC is found most commonly during the second decade and the ratio of female to male is 2:1. ABC's can be found in any bone inthe body. The most common location is the metaphysis of the lower extremity long bones, more so than the upper extremity. The

vertebral bodies or arches of the spine also may be involved. Approximately one-half of lesions in flat bones occur in the pelvis.

Symptoms and Presentation:

Gradually increasing pain, a mass, or with a pathological fracture through the lesion. Rapid increase is lesion size has been

reported in a few cases.

X-Ray Appearance and Advanced Imaging Findings:

On plain film, an ABC is normally placed eccentrically in the metaphysis and appears osteolytic. The periosteum is elevated and

the cortex is eroded to a thin margin.The expansile nature of the lesion is often reflected by a "blow-out" or "soap bubble"

appearance. CT scan can also help delineate lesions in the pelvis or spine where plain film imaging may be inadequate. CT scan

and MRI can narrow the differential diagnosis of ABC by demonstrating multiple fluid-fluid levels within the cystic spaces. MRI

is useful to confirm the multiple fluid-fluid levels and the non-homogeneity of the lesion. ABC appears on both T1 and T2 MRIwith a low signal rim encircling the cystic lesion. A careful search for radiological signs of the precursor lesion, if any, is

recommended. Some of these precursor lesions may have a flocculent chondroid matrix that may be a clue to their pathogenesis.

Laboratory Findings: No relevant findings

Differential Diagnosis: Giant cell tumor, UBC, Telangectatic osteosarcoma

Preferred Biopsy Technique: Incisional / combined with curettage if certainty of diagnosis is high

Histopathology findings:

On gross examination, an ABC is like a blood filled sponge with a thin periosteal membrane. Soft, fibrous walls separate spaces

filled with friable blood clot. Microscopically, the ABC has cystic spaces filled with blood. The fibrous septa have immature

woven bone trabeculae as well as I macrophages filled with hemosiderin, fibroblasts, capillaries and giant cells. The treatmentapproach will vary depending of the location and aggressiveness of the lesion. A slow growing, indolent ABC has been observed

to regress spontaneously. Selective embolectomy of nutrient vessels and percutaneous injection of a fibrosing agent are newer

treatment modalities. Percutaneous injection of methylmethacrylate was used successfully by Herve Deramond for an aggressive

ABC lesion in the second cervical vertebra.

Treatment Options for this Tumor:

Curettage is normally used. Large lesions may require other treatments, such as embolization. The cyst can be packed with bone

chips or polymethylmethacrylate cement. Bone fragility must be addressed with plates, screws, or rods as indicated. Percutaneous

transvascular treatments have be used with good results, and are especially useful in difficult to access lesions of the spine and

skull base.

Preferred Margin for this Tumor: Intralesional

Outcomes of Treatment and Prognosis:Recurrence is seen in approximately 20% of cases and is more common in younger children.

Special and Unusual Features:

One theory of the etiology of primary ABCs is that these lesions are secondary to increased venous pressure that leads to

hemorrhage which causes osteolysis. This osteolysis can in turn promote more hemorrhage causing amplification of the cyst.

Another theory is that these lesions do not arise de novo by rather develop secondarily within another primary tumor such as

osteoblastoma, and subsequently enlarge and destroy all or most of the primary tumor.


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Chondroblastoma

Introduction and Definition:

About 12% of all chondroblastomas occur in the bones of the foot. Chondroblastoma in the foot most commonly occurs in

subchondral areas of the talus and calcaneus as well as the calcaneal apophysis. Chondroblastoma can behave aggressively and

invade soft tissue. Benign pulmonary metastases have been observed.

Incidence and Demographics:Males are affected 6 times as commonly as females. The average age at presentation around 25 years, significantly older than the

average age in other parts of the skeleton.

Symptoms and Presentation:Patients complaint of pain and swelling or a mass near the joint. The pain can be severe. The nearby joint may be locally

inflamed.

X-Ray Appearance and Advanced Imaging Findings:Radiographically, the lesion is located in the exclusively in the epiphysisis, although in the small bones of the foot the location of

the epiphysis may not be obvious. The lesions appear well-defined, expansile, and lucent, and there may be stippled calcification

or there may be no matrix mineralization. The tumor is adjacent to an articular surface or an apophysis. There is a lobular

appearance. CT scan is useful for defining the relationship of the tumor to the joint, the integrity of the underlying bone, and to

identify intralesional calcifications. MRI scans show the very high signal intensity on T2 weighted scans that is characteristic of

cartilage lesions. Bone scan shows avid tracer uptake in the lesion.


Differential Diagnosis: Enchondroma, Central Chondrosarcoma and Aneurysmal Bone Cyst

Preferred Biopsy Technique: Incisional, may be combined with excision in selected cases

Histopathology findings:On gross examination, a chondroblastoma has a lobulated, round form and is made up of friable, soft, grayish pink tissue that may

be gritty. If present, the cystic fluid is rust or straw-colored. Chondroblastoma is made up of uniform, polygonal cells that are

closely packed. These primitive cells are derived from the epiphyseal cartilage plate and have abundant cytoplasm. These cells

have oval shaped nuclei with a prominent groove which has been likened to a coffee bean. There is little mitotic activity. A scant

chondroid matrix may be superimposed by a pericellular deposit of calcification that appears like "chicken-wire". The rapid

proliferation of immature chondrocytes does not create lacunae or formal cartilage matrix. Giant cells are often present.

Treatment Options for this Tumor:Treatment of the primary lesion consists of complete curettage and bone grafting. Extending the zone of the curettage by

removing two or 3 additional millimeters of bone using a mechanical bur, or by using phenol or liquid nitrogen placed in the

tumor cavity have been proposed as in method to reduce the risk of local recurrence.


Outcomes of Treatment and Prognosis:In chondromblastoma of the foot and ankle, recurrence is common, and outcomes are generally worse than in other locations in

the skeleton. The risk of recurrence appears to be highest for lesions located only in the epiphysis, as opposed to lesions in the

apophysis or those that extend into the metaphysis or diaphysis. Recurrence is not definitely related to patient age, sex or

demographic data. Recurrent lesions should be treated with repeat curettage. If a recurrent lesion is located in a readily

reconstructable location, marginal resection with structural allograft or autograft reconstruction is preferable. Recurrence and

severe destruction of bone integrity may necessitate ankle arthrodesis or en-bloc resection with associated functional loss. Patients

with recurrent lesions should have follow-up CT scans of the chest to detect pulmonary nodules. Pulmonary nodules should be

excised.

Suggested Reading and Reference:Fink BR, Temple HT, Chiricosta FM, Mizel MS, Murphey MD. Foot Ankle Int. 1997 Apr;18(4):236-42. Chondroblastoma of the

foot.


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Chondrosarcoma Introduction and Definition:Chondrosarcoma is the most common malignant bone tumor in the foot in some reported series. Patients with multiple cartilage

lesions, such as Ollier's disease, or multiple enchondromas are at increased risk. This tumor has several subtypes, including clear

cell chondrosarcoma, and mesenchymal chondrosarcoma, which can occur in bone (images 1, 2, 3, 4) in the soft tissues (image 5),

where it presents as as an innocent bump. Most chondrosarcomas are low grade, but dedifferentiated chondrosarcoma can occur

in the setting of a longstanding benign cartilage lesion such as enchondroma.


The peak age of presentation is in the 50's and 60's and has a male to female ratio of 1.5 to 1. It is most common in the femur,humerus, ribs and on the surface of the pelvis. Patients with Ollier's disease (multiple enchondromatosis) or Maffucci's syndrome

(multiple enchondromas and hemangiomas) are at much higher risk of chondrosarcoma than the normal population and often

present in the third and fourth decade.

Symptoms and Presentation:The presentation of chondrosarcoma depends on the grade of the tumor. A high-grade, fast growing tumor can present with

excruciating pain. A low grade, more indolent tumor is more likely to present as an older patient complaining of hip pain and

swelling. Pelvic tumors present with urinary frequency or obstruction or may masquerade as "groin muscle pulls" The lesion

presents as a slow growing mass with mild pain.

X-Ray Appearance and Advanced Imaging Findings:On plain radiographs, chondrosarcoma is a fusiform, lytic, lucent defect with scalloping of the inner cortex (which may

demonstrate ring and arc formations ) and periosteal reaction. Extension into the soft tissue may be present (malignant behavior)

as well as punctate or stippled calcification of the cartilage matrix. CT is helpful in defining the integrity of the cortex and

distribution of calcification. MRI is invaluable in surgical planning as it demonstrates the intraosseus and soft tissue involvement

of the tumor. MRI is also helpful in evaluating possible malignant degeneration of osteochondromas by allowing accurate

measurements of the cartilage cap which should be less than 2 cm thick. MRI shows high signal intensity on T2 sequences, and

low intensity signal on T1 sequences. Calcification within the mass, if it occurs, will appear as very low signal areas.

Differential Diagnosis: Osteosarcoma, benign cartilage lesions

Preferred Biopsy Technique: Incisional Preferred Margin for this Tumor: Wide

Histopathology findings:On gross examination, chondrosarcoma is a grayish-white, lobulated mass. It may have focal calcification, mucoid I degeneration,

or necrosis.Histologically, chondrosarcoma is differentiated from benign cartilage growths by enlarged plump nuclei, multiple

cells per lacunae, binucleated cells, and hyperchromic nuclear pleomorphism. Chondrosarcoma is graded from 1 (low) to 3 (high).Low grade chondrosarcoma is very close in appearance to enchondromas and osteochondromas and has occasional binucleated

cells. High grade chondrosarcomas have increased cellularity, atypia and mitoses. There is an inverse relationship between

histologic grade and prognosis with higher grades having a worse prognosis and early metastases.

Treatment Options for this Tumor:Treatment for low grade chondrosarcoma may include curettage or marginal excision. Intermediate and high grade lesions should

be excised with a wide margin. Clear margins are essential, because no truly effective adjuvant therapy exists. Chemotherapy and

radiotherapy are not effective and are normally not used for lesions in the foot. Rather, complete removal with a wide margin is

the correct treatment. Amputation of the affected part is employed if necessary to achieve a wide margin. Incompletely excised

lesions should be referred to a musculoskeletal oncologist for re-resection.


here are three additional types of chondrosarcoma. Mesenchymal chondrosarcoma is a rare variant with a bimorphic histologicpicture of low grade cartilaginous cells and hypercellular small, uniform, and undifferentiated cells that resemble Ewing's

sarcoma. Mesenchymal chondrosarcoma has a predilection for the spine, ribs and jaw and it presents in the third decade. It is

more common in females and can grow exceptionally large. It is very likely to metastasize to lungs, Iymph nodes and other bones.

Clear cell chondrosarcoma is a malignant cartilage tumor that may be the adult variant of chondroblastoma. It is a rare, low-grade

tumor with an improved prognosis over other chondrosarcomas. Likechondroblastoma, it is found in the epiphysis of the femur

and humerus. Histologically, soft tissue invasion is rare. Clear cell chondrosarcoma has clear cells with vacuolated cytoplasm.

The cartilage matrix has significantly calcified trabeculae and giant cells. Dedifferentiated chondrosarcoma is the most malignant

form of chondrosarcoma. This tumor is a mix of low grade chondrosarcoma and high grade spindle cell sarcoma where the

spindle cells are no longer identifiable as having a cartilage origin. The dedifferentiated portion of the lesion may have

histological features of malignant fibrous histiocytoma, osteosarcoma, or undifferentiated sarcoma. This biphasic quality is

evident on x-ray with areas of endosteal scalloping and cortical thickening are contrasted with areas of cortical destruction and

soft tissue invasion. Dedifferentiated chondrosarcoma has a 5 year survival of 10%.


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ChondromyxoidFibromaIntroduction and Definition:

This rare benign tumor has a striking predilection for the bones of the tibia and the foot. About one quarter of all of these tumors

involve the foot, with the metatarsals the most common location.


Most patients are younger than 30. It is more common in males, typically in the second or third decade of life.

Symptoms and Presentation: Patients present with pain and a slow growing mass.

X-Ray Appearance and Advanced Imaging Findings:Radiological findings demonstrate an eccentrically placed Iytic lesion with well defined margins in the metaphysis of the lower

extremity. The lesion usually has a sclerotic margin of bone and a lobulated contour. Ridges and grooves that appear in the

margins secondary to scalloping falsely appear to be trabeculae. CT helps define cortical integrity and confirms that there is no

mineralization of the matrix, unlike other cartilage tumors. CMF has the same appearance on MRI as other cartilage tumors which

is decreased signal on T 1 weighted images and increased signal on T2 weighted images. MRI is helpful in preoperative planning

and staging. CMF resembles fibrocartilage grossly. It has a sharp border often with an outer surface of thin bone or periosteum.

The glistening grayish white lesion is firm and lobulated. It may also have small cystic foci or areas of hemorrhage.


Differential Diagnosis:The radiologic differential diagnosis includes giant cell tumor, aneurysmal bone cyst, juxtacortical chondroma, unicameral bone

cyst, chondroblastoma and fibrous dysplasia

Preferred Biopsy Technique:

Careful biopsy and evaluation by an experienced pathologist are necessary to distinguish this tumor from similar aggressive or

malignant lesions. Curettage may be adequate, but may result in local recurrence in as many as a quarter of patients.


Histologically, CMF appears very similar to chondrosarcoma. They are so close in histology that often radiology helps to make

the final diagnosis. The predominant features of CMF are the zonal architecture and lobular pattern. Nodules of cartilage are

found in between fibromyxoid areas. In some fields the loose myxoid dominates and in other the dense chondroid dominates. The

chondrocytes are plump to spindly in shape and have indistinct cell borders in sparsely cellular lobules of myxoid or chondroid

matrix. There are also more cellular zones of the tumor with some giant cells at the edges. The sharp borders of each lobule andthe lesion itself help to differentiate it from chondrosarcoma.

Treatment Options for this Tumor:Marginal or wide excision and substitution of the involved bone with a structural bone graft is usually curative.

Outcomes of Treatment and Prognosis:

Unlike giant cell tumor, this tumor has a propensity to recur due to seeding of the soft tissues during curettage. Local recurrence

can be treated with meticulous repeat curettage and excision of the entire soft tissue mass. Marginal or wide excision and

substitution of the involved bone with a structural bone graft is usually curative.


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CASE:ChondromyxoidFibromaA 13-year-old boy presents to the orthopedic outpatient department (OPD) with a 1.5-year history of mild,recurrent pain in his left lower leg with recent exacerbation of the pain after a trivial trauma during outdoor

activity. He has no history of any systemic symptoms, such as fever, or any other significant past medicalhistory. There is no significant family medical history.

The patient is a well-built, athletic-appearing boy. His blood pressure is 116/78 mm Hg, his pulse rate is 68 bpm, and his body temperature is measured at 98.2F (36.8C) during his first visit to the OPD.

Examination of the leg reveals severe localized tenderness over the lower left tibial prominence, with soft-

tissue swelling and edema. According to the patient, he has been feeling mild fullness over the left medialmalleolus for more than 1 year, without it causing much pain. The overlying skin shows mild reddening as

well as increased local temperature. The cardiovascular, respiratory, and gastrointestinal organs examined

clinically are within normal physiologic limits.

The hematologic and biochemical parameters examined are within normal physiologic limits. The

erythrocyte sedimentation rate and C-reactive protein levels are also within normal physiologic limits. Thehematologic examination shows a hemoglobin level of 11 g/dL, total leukocyte count of 13,000 x 10

3/L

and a platelet count of 180 x 10

3

/L. An anteroposterior chest x-ray does not show any localized lesions inthe lungs. No lymphadenopathy is detected. Anteroposterior- and lateral-view x-rays of the lower left end ofthe tibia show an eccentrically located, well-demarcated, lytic, bubbly, lobulated lesion in the metaphyseal

region (Figure 1). A periosteal reaction is not seen. Focal epiphyseal extension is also noted (Figure 2). A

subtle fracture is identified at the lateral margin of the lower tibia (Figures 1 and 2). Axial T2-weighted MRIalso shows a hyperintense solid lobulated growth (Figure 3). A biopsy is performed, but unfortunately the

yield is scant and is comprised only of fibrous tissue and traces of cartilaginous material. Curetting and bone

grafting is performed, with the corresponding histopathologic examination demonstrating a characteristic biphasic lesion (Figure 4). A frozen section prepared from the curettage shows a possible benign

cartilaginous tumor.


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The x-rays and MRI of the left lower tibia demonstrated features of a chondromyxoid fibroma (CMF) with

fracture of the lower end of the tibia. Grossly, the specimen demonstrated multiple grey-white fragments,

with focally identifiable firm periosteal bone attached over the fragments. The cut surface of the fragmentsshowed a shiny myxoid appearance with intervening firm grey-white areas. Histopathologic examination

showed a lobulated lesion. The lobules of chondromyxoid materials were separated by thin cellular septae

comprised of innocuous-looking spindle cells with interspersed small vessels and few osteoclastic giantcells. The chondromyxoid component showed varying cellularity. The periphery of the lobules was more

cellular in appearance, and the cells were predominantly spindle in shape. In the center, the cells had amoderate amount of eosinophilic cytoplasm, while a few others were stellate-shaped. Chondrocytes werealso identified. There was no evidence of multinucleation within the lacunae or significant nuclear

pleomorphism. The spindle-cell component also did not show any pleomorphism or mitotic activity (Figure

4). These features, correlated with the radiologic findings, were indicative of CMF.

CMF is a benign tumor of bone that was first described by Jaffe and Lichenstein in 1948.[1,2]

This lesionaccounts for 1% of all bone tumors and 2% of all benign bone tumors.

[3]It is most commonly found in the

long tubular bones, especially the tibia and femur near the knee joint; however, the overall most common

site is the proximal tibia, which is affected in 30% of cases. Approximately 25% of cases occur in the flatbones.

[3,4]The small bones of the lower limbs may also be affected. The skull, spine, and bones of the upper

extremity are relatively uncommon sites for this lesion. Patients with this condition range from 3 to 70 yearsof age; most cases, however, are seen in patients between the ages of 10 and 30 years. A male predominancehas been described (male-to-female ratio, 2:1).

[3,5]The most common presenting symptoms are pain and

swelling, which are noted in 85% and 65% of cases, respectively; the third most common symptom is

restriction in joint movement. The pain is usually mild, transient, and of long duration.[6]

Approximately

15% of cases are discovered incidentally on radiologic examination. Pathologic fracture may occur in 5% of

cases, causing significant morbidity.

Plain x-rays are very useful when this lesion is suspected; however, histopathologic examination is

mandatory for confirmation of the diagnosis. Bubbly lesions are typical in the metaphysis, and when seen, adifferential diagnosis of giant cell tumor, aneurysmal bone cyst, and CMF should always be kept in mind.

The possibility of an osteosarcoma should also be considered. The bubbly pattern is usually caused byridging or endosteal scalloping of the surrounding host bone. Histologically, the possibility of a low-gradechondrosarcoma should also be carefully ruled out. Because of the nodular growth pattern of any

cartilaginous tumor, the histologic diagnosis is primarily based on the extent of cellularity and the cytologic

atypia of the tumor cells. Mild-to-moderate cytologic atypia, however, has also been described in CMF;

therefore, the extent of cellularity, multinucleation within the lacunae, and the presence of atypical mitoticactivity in the tumor should be relied upon as features to rule out chondrosarcoma. In this context, it is also

important to remember that the periphery of the nodules in CMF show marked cellularity and should prompt

histopathologists to concentrate on the center of the lobules when assessing the criteria of cellularity. CMF,like osteosarcoma, shows erosion of cortical bone with soft tissue infiltration. Osteoid production by the

tumor cells is also characteristic of this lesion. Radiologic correlation is mandatory because CMFs are

typically bubbly, oval in shape, and have a long axis parallel to that of the long bone. Extension intodiaphysis or epiphysis is not uncommon.

[5,7]Unlike other cartilaginous tumors, calcification is less frequent

and the margins are typically scalloped. An MRI scan may help to resolve minute details, such as soft tissue

extension. T2-weighted MRI will show a hyperintense, homogeneous lesion (Figure 3). CT scans may help

to identify any calcifications within the lesion, which are uncommon and occur in about 2% of cases.[5,7]

The histogenesis of CMF is uncertain and is a matter of continuing speculation. The cartilaginous origin, as

apparent on the morphologic features, has been supported by ultrastructural studies and by

immunohistochemical stains for S-100 protein. Because of their occasional immunopositivity for smoothmuscle actin and S-100 proteins, possible myofibroblastic, myochondroblastic, and chondrocytic

differentiation was suggested.[7]

Due to the same reasons, a possible resemblance with chondroblastoma was


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cited; however, this finding was not subsequently substantiated by other studies. Others showed osteocalcin

reactivity, which is seen in greater than 50% of CMFs, as a cause to support its link with other bone and

cartilage tumors, especially chondroblastomas.[7]

A study by Romeo and colleagues[8]

examined the DNAmicroarray of CMF and found that the differential expression of adhesion and extracellular matrix

molecules, including CD166, versican, perlecan, and Col4A2, may interfere with normal cartilaginous

differentiation and lead to the development of CMF. There are some studies indicating a possiblecartilaginous derivation by examining the expression of transcription factor SOX9 in the tumor cell nuclei,

along with high expression of collagen type II in the cell cytoplasm. A low (< 5%) MIB-1 proliferationindex also supports its indolent character. Although many cytogenetic abnormalities have been reported inCMF, t(1;5)(p13;p13) is a novel clonal cytogenetic abnormality in CMF and has diagnostic significance.

Other frequent chromosomal abnormalities described are aberrations in chromosomes 2 and 5.[7]

The prognosis in cases of CMF is usually excellent, even when there is recurrence.[5]

Treatment of the lesion

includes curettage oren bloc excision with bone grafting. Radiotherapy is contraindicated because it causesdedifferentiation and malignancy. In cases of multiple recurrence, radiotherapy may be of some help.

[9]

Recurrence has been reported in 3%-22% of cases, especially within the first 2 years of surgery, but it has

been reported 30 years after surgery as well.[10]

Recurrence is more frequently seen in patients younger than15 years of age with a more myxoid tumor with nuclear atypia. Some reports have not found any correlation

between the histologic findings and recurrence in CMF. Metastasis has never been reported.[5]

All of thesefacts point to the need for long-term follow-up in these patients.

[11]

In the patient in this case, curettage of the lesion with bone grafting was performed. Local extension of thelesion into the articular cartilage and the scant yield of the preintervention biopsy dictated the decision to

opt for curettage, followed by fracture fixation. Care should be taken to curette the whole lesion when

performing this treatment because incomplete curettage is one of the important factors leading to localtumor recurrence. The patient has had 2 monthly follow-up examinations over a period of 8 months, with no

recurrence detected.

1. Jaffe HL, Lichtenstein L. Chondromyxoid fibroma of bone: a distinctive benign tumor likely to be mistakenespecially for chondrosarcoma. Arch Pathol (Chic). 1943;19:541-551.2. Wu CT, Inwards CY, O'Laughlin S, Rock MG, Beabout JW, Unni KK. Chondromyxoid fibroma of bone: aclinicopathologic review of 278 cases. Hum Pathol. 1998;29:438-446.

3. Ostrowski ML, Spjut HJ, Bridge JA. Chondromyxoid fibroma. In: Fletcher CDM, Unni KK, Mertens F,eds. World Health Organization Classification of Tumors. Pathology and Genetics of Tumors of Soft

Tissue and Bone. Lyon: IARC Press; 2002:243-245.

4. Desai SS, Jambhekar NA, Samanthray S, Merchant NH, Puri A, Agarwal M. Chondromyxoid fibromas: astudy of 10 cases. J Surg Oncol. 2005;89:28-31.

5. Fechner RE, Mills SE. Tumors of bones and joints. In: Atlas of Tumor Pathology. Fascicle 8, 3rd series.Washington, DC: Armed Forces Institute of Pathology; 1993:95-100.

6. Tallini G, Dorfman H, Brys P, et al. Correlation between clinicopathological features and karyotype in 100cartilaginous and chordoid tumors. A report from the Chromosomes and Morphology (CHAMP)

Collaborative Study Group. J Pathol. 2002;196:194-203.

7. Armah HB, McGough RL, Goodman MA, et al. Chondromyxoid fibroma of rib with a novel chromosomaltranslocation: a report of four additional cases at unusual sites. Diagn Pathol. 2007;2:44.

8. Romeo S, Oosting J, Rozeman LB, et al. The role of noncartilage-specific molecules in differentiation ofcartilaginous tumors: lessons from chondroblastoma and chondromyxoid fibroma. Cancer. 2007;110:385-

394.9. Baujat B, Attal P, Racy E, et al. Chondromyxoid fibroma of the nasal bone with extension into the frontal

and ethmoidal sinuses: report of one case and a review of the literature. Am J Otolaryngol. 2001;22:150-

153.

10. Danielsen B, Ritzau M, Wenzel A. Recurrence of chondromyxoid fibroma: a case report. DentomaxillofacRadiol. 1991;20:265-267.

11. Kikuchi F, Dorfman HD, Kane PB. Recurrent chondromyxoid fibroma of the thoracic spine 30 years afterprimary excision: case report and review of the literature. Inter Int J Surg Pathol. 2001;9:323-329.


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EnchondromaIntroduction and Definition:

Approximately 8% of these tumors occur in the bones of the foot. Small, peripheral cartilage tumors tend to be benign, where as

large central cartilage lesions are more likely to be malignant. Reliable differentiation of benign from malignant cartilage tumors

is difficult. Tumors that are larger, tumors located in the hindfoot or midfoot, or new tumors presenting in a patient with a known

history of enchondromatosis (Ollier's disease) have an increased risk of malignancy.


The peak age at diagnosisis around the middle of the fourth decade, but the tumor may present as virtually any age

Symptoms and Presentation:Patients present with pain during activities or after an injury, but there is rarely any mass palpable on physical examination. For

enchondromas in the phalanges, pathological fracture through the lesion will cause the patient to seek medical care. A few

patients have multiple enchondromas and warrant special attention and possibly referral to a bone tumor specialist.


Enchondroma usually occurs in the metatarsals or phalanges of the lesser toes. The hindfoot is rarely involved. The lesion is

typically a solitary, slightly expansile,lucent lesion with minimal matrix calcification, that may thin, expand, or fracture the

nearby cortex. Radiographically, the lesion is expansile and lytic, with a variable amount of matrix mineralization. The matrix has

been described as "popcorn" or "stippled". The matrix consists of nodules of cartilage which tend to calcify at the periphery, so

that on high quality radiographs "ring and arc" forms are visible. Clear demonstration of these helps confirm the diagnosis so that

biopsy is not necessary. Other radiological findings such as the presence or absence of matrix mineralization, amount and extent

of cortical thinning or expansion, and findings on technetium bone scans do not seem to be well correlated with the presence or

absence of malignancy.

Differential Diagnosis:Juxtacortical chondroma, chondromyxoid fibroma. Giant cell tumor may be mistaken for enchondroma, and both can occur in the

foot in similar locations. GCT has no matrix calcification and occurs exclusively in the metaphysis and epiphysis adjacent to the

growth plate, often extending right up to the joint surface. In small bones that are completely filled with tumor, these lesions may

be difficult e to differentiate. The MRI signal patterns are distinct. Treatment is very different so the surgeon should be careful to

make an accurate diagnosis.

Preferred Biopsy Technique: Open, combined with excision after frozen section

Histopathology findings:On gross examination, an enchondroma consists of bluish-gray lobules of fine translucent tissue. The degree of calcification of

the lesion determines if the consistency is gritty.Under the microscope, a thin layer of lamellar bone surrounding the cartilagenodules is a positive sign that the lesion is benign. At low power, there are lobules of different sizes. Blood vessels are surrounded

by osteoid. Enchondromas have chondrocytes without atypia inside hyaline cartilage. The nuclei are small, round and pyknotic.

The cellularity varies between lesions and within the same lesion. Each potential enchondroma needs to be evaluated for

cellularity, nuclear atypia, double nucleated chondrocytes and mitotic activity in a viable area without calcifications to distinguish

it from low-grade chondrosarcoma. Small peripheral lesions are more likely to be benign than large axial lesions. The pathologic

diagnosis is so difficult it always needs to be made in conjunction with the radiologist and the surgeon

Treatment Options for this Tumor:Treatment depends on how expansile the lesion has become. Lesions inside the medullary cavity may remain totally latent, are

usually asymptomatic, and no treatment other than intermittent radiographic follow-up is indicated. If a medullary enchondroma

requires biopsy for some reason, it can be curetted at the same time and the defect filled with an apropriate bone void filler.

Extremely expansile lesions may require complete excision and substitution of a structural allograft. In the foot, these lesions can

cause cosmetic and functional loss and pathological fracture. Large lesions in the distal phalanges should be considered for partial

amputation of the toe, since the functional and cosmetic result of curettage and bone grafting may be unacceptable.



Enchondromas recur very rarely following treatment, so that total eradication of the lesion is not necessary, rather the goal should

be is restoring appearance and function. Curettage and bone grafting is usually adequate.


Enchondroma may be highly expansile, especially in small bones such as the phalanges, so that the bone may be completely

involved, deformed, and even destroyed. This is not considered a sign of malignancy in enchondromas of the foot or hand. This

same behavior seen in a long bone such as the femur or humerus would be interpreted as a strong suggestion of malignancy.


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EwingsSarcomaIntroduction and Definition:

Ewing's sarcoma is a highly malignant tumor that is a type of peripheral primitive neuroectodermal tumor (PNET). Ewing's sarcoma is

found in the lower extremity more than the upper extremity, but any long tubular bone may be affected. The most common sites are

the metaphysis and diaphysis of the femur followed by the tibia and humerus. Ewing's sarcoma occurs in every bone of the foot

About one-third are located in the hindfoot, and 20% of the total occur in the calcaneous. Ewing's of the foot is a highly aggressive

tumor with frequent metastasis. A complete cancer staging work-up is required and a carefully planned biopsy should be the last step

in the sequence.

Incidence and Demographics: Ewing's sarcoma is most common in the first and second decade. The ratio of male to female is 3:2

The mean age at diagnosis of patients with tumors in the foot is 17 years.


Patients normally have pain accompanied by significant diffuse swelling. The area may appear inflamed and a misdiagnosis of

infection can be made. The white blood cell count, erythrocyte sedimentation rate and temperature may all be moderately elevated.

Patients have symptoms for an average of 14 months prior to diagnosis. Patients with hindfoot lesions have an average duration of

symptoms of 22 months prior to diagnosis, whereas those with forefoot lesions have an average duration of symptoms of seven

months.


Radiologically, Ewing's sarcoma is often associated with a lamellated or "onion skin" periosteal reaction. This appearance is caused by

and splitting and thickening of the cortex by tumor cells. The lesion is usually lytic and central. Endosteal scalloping is often present

The "onion-skin" appearance is often followed with a "moth-eaten" or mottled appearance and extension into soft tissue. Bone marrow

infiltration is not obvious on plain x-ray. The radiologic appearance of Ewing's sarcoma in the foot is highly variable. The tumor maypresent as a small lytic lesion with a permeative appearance and no matrix or soft tissue calcification. In other cases the lesion causes

permeative lysis accompanied by marked sclerosis. In an unusual case involving the distal fibula, the lesion appeared entirely cystic

and was mistaken for a unicameral (simple) bone cyst. Bone scan shows abnormal uptake, which may be intense. CT scan

demonstrates the permeative destruction well. MRI is essential for surgical planning and demonstrates the soft tissue extent of the

mass, which may be characteristically extensive; on TI-weighted images the tumor has low intensity compared to the normal high

intensity of bone marrow. On 1:2 -weighted images the tumor is hyper intense compared to muscle. Ewing's sarcoma has increased

uptake on bone scan.

Differential Diagnosis: Infection, neuroblastoma metastasis, lymphoma, leukemia.

Preferred Biopsy Technique: Open biopsy for bone lesions, core or tru-cut is often adequate for soft tissue lesions

Preferred Margin for this Tumor: Wide

Histopathology findings:Grossly, the tumor is gray to white in color and poorly demarcated. The consistency is soft and gray and sometimes semi-liquid

especially after breaking through the cortex. Areas of hemorrhage and necrosis are common. The destruction is often greater on gross

appearance than was visible on radiographs.Under the microscope, Ewing's sarcoma consists of densely packed uniform small cells in

sheets. The cells have scant cytoplasm without distinct borders. The cells are two to three times as big as lymphocytes and have a

single oval or round nucleus without prominent nucleoli. The tumor spreads through Haversian canals which cause the appearance of

permeative margins on x-ray. Glycogen is present within the cells causing a positive reaction to periodic acid-schiff (PAS) stain. Mos

Ewing's sarcomas are positive with HBA-71 or 0-13 stain which is an antibody to the protein product of myc 2. The microscopic

differential includes lymphoma and metastatic neuroblastoma which must be excluded by reticulin stain and urine vanillyl mandelic

acid and homovanillic acid respectively. Rhabdomyosarcoma is ruled out if the specimen stains negatively with desmin, myoglobin

and actin stains. A neural origin is supported by electron microscope findings of pseudorosettes. This is further supported by the

common finding in Ewing's sarcoma and primitive neuroectodermal tumors of choline acetyltransferase and the translocation

t(11:22)(q24;ql2). It is thought that Ewing's sarcoma with its few organelles is the poorly differentiated end of the spectrum of PNET

Neuroepithelioma is an example of well differentiated PNET and has neurosecretory granules and neuritic processes

Treatment Options for this Tumor:Treatment consists of chemotherapy, radiation therapy, and surgical resection depending on stage and extent of disease. Ewing's

sarcoma in the foot with regional metastasis can be treated with radiation of the primary, resection and radiation for the metastasis plus

chemotherapy in order to balance the positive and negative effects of treatment in the setting of a relatively poor prognosis.

Outcomes of Treatment and Prognosis:Survival is highly dependant on the stage of the disease and may also vary according to location. Patients without metastasis had 88%

survival, whereas those with non-pulmonary and pulmonary metastasis had 10% and 0% survival, respectively. Patients with tumors

in the forefoot had 70% survival and those with tumors in the hindfoot had 33% survival. Tumor size and delay before diagnosis also

vary by site, and these factors are likely to have a greater impact on prognosis than the difference in site alone.


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GanglionicCystIntroduction and Definition:

The origin of ganglion cysts is unclear but they are commonly associated with degenerative conditions of

soft tissue or bone. They may occur adjacent to joints, tendons, fascial planes, and within bone.


Most ganglion cysts can be definitively diagnosed based on a careful history and physical examination. Byhistory the lesion has a tendency to both increase and decrease in size over time. On exam, ganglion cyst

typically has superficial location, and may be adjacent to a joint. When these lesions occur near a joint, there

is often osteoarthritis seen on the xray. The mass is soft when the nearby joint is relaxed, and becomes firm

when the nearby joint or muscle is tensed. A pen light or a small laser pointer will transilluminate the cyst.


Most ganglion cysts can be definitively diagnosed based on a careful history and physical examination. By

history the lesion has a tendency to both increase and decrease in size over time. On exam, ganglion cyst

typically has superficial location, and may be adjacent to a joint. When these lesions occur near a joint, there

is often osteoarthritis seen on the xray. The mass is soft when the nearby joint is relaxed, and becomes firm

when the nearby joint or muscle is tensed. A pen light or a small laser pointer will transilluminate the cyst.


If the initial assessment yields the expected results, one attempt at aspiration with a large bore needle should

be performed. Aspiration of the characteristic clear viscous material from the mass confirms the diagnosis.

If the characteristic fluid is not obtained, no further attempts should be made


Once confirmed, the cyst may be treated with aspiration and injection with cortisone, which should lead to

resolution in about half the cases. Surgical removal is indicated for persistent, large or troublesome cysts.

The mass should explored and the origin of the cyst and the stalk identified, if possible. A portion of the

joint capsule and the stalk should be excised in continuity with the mass. Loupe magnification andtourniquet hemostasis will assist in visualization of the stalk and may decrease the risk of recurrence.


Approximately 10% of these cysts recur following surgery.


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GiantCellTumorofTendonSheathIntroduction and Definition:Giant cell tumor of tendon sheath is a rare, solitary benign soft tissue tumor which may arise in the tendon sheath tissues around the

ankle and the toes of the foot. Most cases occur in the hand, where local recurrence after excision has been reported in up to 40% of

cases. Approximately 3 - 10% of these tumors occur in the foot, most commonly in the forefoot, especially the great toe.

Incidence and Demographics: Most patients are young adults, around age 30.

Symptoms and Presentation:Clinically, the patients report a slow growing painless, firm solitary mass adjacent to the dorsal or plantar tendons, the midfoot joints,

or the ankle joint, which has been present for one to two years on average. There may be a history of trauma, and neurological

symptoms occur rarely. In one study, lesions in the forefoot occurred in the first, second, and fifth rays exclusively, indicating that

there may be some relationship between weight-bearing and this tumor. The tumor may cause or accentuate an angular deformity such

as hallux valgus.


On plain radiographs, there may be a visible soft tissue swelling, sometimes completely encasing the bony elements of the involved

digit, and the tumor may invade the adjacent bone and cause cystic lesions that are clearly visible on xray. Approximately 10%

involve bone. The bone involvement and destruction leads to concern for primary bone malignancy, and inappropriately aggressive

treatments can result. CT scan will show the extent of the tumor, and clearly delineate any bony involvement. Some of these tumors

have small calcifications, feature shared with synovial sarcoma. MRI scans are helpful to define the extent of the lesion, and can be

helpful in the preoperative diagnosis. Hemosiderin in the lesion may result in vary low signal intensities on some sequences, and the

lesions enhance on T1 sequences after administration of gadopentetate contrast agent, and these features help identify the tumor

Differential Diagnosis:

Based on the location, age, and invasiveness of the tumor, the differential diagnosis may include a large number of benign and

malignant lesions, including synovial sarcoma, chondromyxoid fibroma, enchondroma and chondrosarcoma, giant cell tumor, and

pigmented villonodular synovitis. Due to be overlapped between the clinical and radiological features of this tumor and that of certain

sarcomas, healthcare providers that are not tumor specialist should take great care in managing patient's home they suspect have giant

cell tumor of tendon sheath

Preferred Biopsy Technique: An open, separate, staged biopsy is strongly recommended

Preferred Margin for this Tumor: Marginal

Histopathology findings:A separate, staged biopsy is strongly recommended. The lesion cannot always be characterized by the preoperative studies, and

aggressive or destructive features may be present that are also consistent with malignancy. Open surgical biopsy with frozen sectionanalysis is preferred, performed through a well planned longitudinal incision that avoids any involvement of nearby neurovascular

structures. If the lesion can be characterized by MRI, and the level of confidence in the preoperative diagnosis is very high, then

excisional biopsy is appropriate. Grossly, the lesion is a nodular, multilobulated soft tissue mass 1-3 cm in size, although neglected

cases may be larger. Histologically, the lesion is similar to pigmented villonodular synovitis. There is hemosiderin and frequent

macrophages, foam cells, and scattered giant multi-nucleated cells. The origin of the tumor is unclear. DNA aneuploidy, chromosoma

translocations, and tumor expression of p63 and nm23 have been reported in a variable proportion of cases. Expression of p63, has

been identified in giant cell tumor of bone, pigmented villonodular synovitis, and the giant cell tumor of tendon sheath, leading to

speculation that these may share a common origin. The giant cells in all 3 of these tumors have been found to demonstrate features

that are associated with osteoclast, including tartrate- resistant acid phosphatase marking, and calcitonin receptor expression

Treatment Options for this Tumor:Treatment is by complete, meticulous excision of the entire lesion. A wide a radical margin is not necessary. Intralesional margins are

acceptable, as long as complete excision is not compromised. Recurrence has been reported in up to 45% of cases, but with careful

removal, recurrence can be reduced to 10 to 20%. In the lesser toes, where the lesion has extensively invaded the soft tissues and bone

amputation may be preferable to excision. In the great toe, efforts should be made to preserve the mechanical integrity of the first ray

including complete meticulous excision of the lesion, followed by bone grafts, skin grafts, and fusions as necessary.

Outcomes of Treatment and Prognosis:In the office experience, initial treatment of these lesions is often by partial resection and recurrence is common. When the lesion

extensively involves the local anatomy, the resection may lead to compromise of neurovascular status. However, it may be preferable

to save a partially insensate digit rather than resort to amputation. In most cases, meticulous marginal resection leads to preservation of

the digit with good function.


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GiantCellTumorIntroduction and Definition:Giant cell tumor is a benign but locally aggressive tumor that can occur in any bone. Giant cell tumor accounts for 5 to 9 percent of al

primary bony tumors. Giant cell tumors are usually found in the long bones, most often the distal femur, proximal tibia, and dista

radius. Whether that tumor arises in the epiphysis or distal metaphysis is a matter of controversy, but giant cell tumors only occur afte

the epiphyseal plates have closed and a diagnosis of GCT in a patient with open growth plates should be questioned. This tumor is

uncommon in the foot. The lesions are located in the metaphysis adjacent to the epiphysis or epiphyseal scar. For this reason, the

lesions are located proximally in the first metatarsal and distally in the lesser metatarsals due to the location of the epiphysis. The

tumor can cross joints and affect several adjacent bones. In time, the cortex may be expanded and even destroyed. In smaller bones,

the lesion can slowly expand the entire bone into an oversized balloon with cartilage on the end. It is believed by some to be

potentially malignant. In the very rare instances this lesion has the potential for metastasis to the lungs and in these cases the lung

lesions may behave in an indolent fashioned and even require no treatment. The authors recommend a chest CT scan for all patients

newly diagnosed with GCT.

Incidence and Demographics: It possibly is the most common bone tumor in the young adults aged 25 to 40. Giant cell tumor is

found more commonly in women than men, and occusr most often during the third decade.

Symptoms and Presentation:Most patients present with slowly progressive pain, with or without a mass. Symptoms arise when the lesion begins to destroy the

cortex and irritate the periosteum or when the weakening of the bone caused by the tumor causes pain due to imminent pathologic

fracture. Some giant cell tumors present with a pathologic fracture.


Plain radiographs show a lytic lesion without matrix mineralization most often eccentrically placed to the long axis of the bone. Theepicenter is in the metaphysic and is most radiolucent with increasing density towards the periphery. There is a well-defined in defect

in the metaphysis and epiphysis, with destruction of the medullary cavity and adjacent cortex. The tumor expands into the epiphysis

until it reaches the subchondral bone, which seems to be a partial barrier to further growth. Intact borders and a sharp inner margin

may be associated with a better prognosis. These tumors often thin the cortex, and may expand into the soft tissues surrounding the

bone, or they may expand the bone extensively, remaining within an eggshell-thin rim of periosteal new bone.



Preferred Margin for this Tumor:

Histopathology findings:The gross appearance of the giant cell tumor is pain and, firm, and homogeneous, with foci of hemorrhage or necrosis.

Microscopically, there are numerous multinucleated giant cells. The stromal cells are homogeneous mononuclear cells with around orovoid shapes, large nuclei and indistinct nucleoli. The nuclei of the stromal cells are identical to the nuclei in the giant cells, a feature

that distinguishes giant cell tumors from other lesions that also contained giant cells. Another feature of giant cell tumor is that the

giant cells may contain very large numbers of nuclei, often several hundred. In some tumors, the giant cells can be seen to be

engulfing more nuclei from the stroma

Treatment Options for this Tumor:Treatment of giant cell tumors is by surgery only. Intralesional excision by "extended" curettage is the treatment of choice. Curettage

alone is associated with a high recurrence rate, and this can be decreased with the addition of chemical cautery using phenol, multiple

freeze-thaw cycles using liquid nitrogen, and treating the walls of the cavity with a high-speed rotary burr. Local recurrence after

curettage alone is thought to lead to recurrence in 50% of cases. Recurrence after extended curettage is approximately 10 percent. The

tumor cavity may be filled with polymethyl methacrylate cement or bone graft, according to the surgeon's preference. Some believe

that the polymethyl methacrylate cement lowers the risk of a local recurrence due to the large amount of heat given off during

hardening. Recurrences are normally treated with a second interlesional surgery. Bone graft may allow for more favorablebiomechanics of load inthe nearby joint. The early signs of local recurrence may be more difficult to detect in cases treated with bone

graft. Lesions that are highly expansile and destructive, or lesions that occur in "expendable" bones such as the proximal fibula (shown

here) may be excised with a wide margin. Multiply recurrent giant cell tumors are also treated with wide resection. Giant cell tumor

may occur in the sacrum, a site where complete surgical excision is very difficult. Intralesional removal of as much of the lesion as

possible followed by radiation to the tumor site has been associated with acceptable tumor control. There is concern about secondary

malignancy arising in irradiated giant cell tumors. A variety of reconstructive methods are utilized depending on the extent of bony

defect, or no reconstruction may be necessary. Chemotherapy is not used.


Following surgery, patients should be made aware of the ongoing risk of local recurrence. Patients should be followed on a regular

basis for the first 2 years at least. Local recurrence of giant cell tumor should trigger a complete workup including CT scan of the

chest, abdomen and pelvis.


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Glomus Tumor

Introduction and Definition:Glomus tumor is a rare and benign vascular tumor. The normal glomus unit is a neuromyoarterial apparatus that functions to

regulate skin circulation and is found subungually, on the finger tip pulp, on the base of the foot and the rest of body in

descending order. The most common site of glomus tumors is subungual and 75% of the lesions occur in the hand. Other sites

include the palm, wrist, forearm and foot. Glomus tumor can occur near the tip of the spine, where it may arise from the glomus

coccygeum. Glomus tumors have also been described in locations where the glomus body does not normally occur. Unusual sites

include the patella, bone, chest wall, eyelid, colon, rectum, cervix, and other sites. Glomus tumors rarely arise directly from bone.

Incidence and Demographics:The lesions present most frequently during the fourth and fifth decade of life although they can be found in any age and at any

site. The subungual tumors affect women three times more commonly than men.

Symptoms and Presentation:Clinically, glomus tumors are characterized by a triad of sensitivity to cold, localized tenderness and severe intermittent pain. The

pain can be excruciating and is described as a burning or bursting.The exact cause of the pain is not completely understood, but

nerve fibers containing the pain neurotransmitter substance P have been identified in the tumor.

X-Ray Appearance and Advanced Imaging Findings:Radiologically, glomus tumors appear as well circumscribed osteolytic lesions. The lesion shows either bone erosion or invasion

depending on where it arises. A sclerotic border is present due to the slowly enlarging mass. CT scan shows a non-specific

subungual mass. T1 MRI is not as useful for subungual lesions as it only demonstrates a dark, well delineated mass. Glomus

tumors appear as a very high and homogeneous signal intensity on T2 weighted images. MRI is useful for the detection of lesionsin the soft tissues. The radiological differential includes epidermal inclusion cyst, enchondroma, chronic osteomyelitis,

sarcoidosis, metastatic carcinoma, subungual melanoma and osteoid osteoma




Histopathology findings:Grossly, the tumors are usually less than one cm. in size, and appear as small red-blue nodulas. The lesion appears as a localized

dark red or blue lesion beneath the finger nail, but the subungual lesions can be difficult to detect on clinical examination.

Radiographs of the distal phalanx show a small scalloped osteolytic defect with a sclerotic border. Under the microscope, glomus

tumors are found at the dermal and subdermal junction and have a fibrous capsule. They are made of an afferent arteriole,

anastomotic vessel, and collecting venule. These vascular structures are surrounded by rounded uniform epithelioid cells withgranular cytoplasm known as glomus cells or pericytes. Also present are smooth muscle cells and non-myelinated nerve cells.

There is no pleomorphism or mitotic activity. There are three forms of glomus tumors: vascular, myxoid and solid. The vascular

form consists of mostly vessels with little epithelioid component. The solid form has sheets of glomus cells with few vessels.

Glomus tumors stain positive for the smooth muscle marker actin

Treatment Options for this Tumor:Treatment of glomus tumors consists of surgical excision. Repair of the nail bed must be performed after the removal of

subungual lesions.

Outcomes of Treatment and Prognosis:Relief of pain is usually intermediate after surgery.


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OsteoblastomaIntroduction and Definition:Osteoblastoma is a solitary, osteoid producing benign bone lesion which can demonstrate aggressive clinical behavior.

Osteoblastoma and osteoid osteoma are histologically very similar, yet these two tumors are very different in their presentation,

localization, radiographic appearance, treatment, and potential for recurrence. The foot is the 3rd most common location of

osteoblastoma after the spine and the femur. 12.5% of osteoblastoma occur in the bones of the foot. Most occur in the hind foot,

and the talus is most commonly affected bone. In one review of 41 osteoblastomas in the foot, two evolved into malignant

sarcomas.


Osteoblastoma predominantly affects young adults. The peak age of occurrence is approximately age twenty, though the tumor

may present as early as age ten to as late as age sixty.

Symptoms and Presentation:Common symptoms are pain of long duration, swelling and tenderness. Tumors of the spine can cause scoliosis and neurological

symptoms. The lesion may clinically present with myleopathic and/or radicular symptoms.

X-Ray Appearance and Advanced Imaging Findings:On x-ray, osteoblastomas appear as a radio-lucent defect with a central density due to ossification. The lesion is well

circumscribed and may have a surrounding sclerosis. The tumor demonstrates increased isotope uptake on bone scan.

Differential Diagnosis: osteoid osteoma, osteosarcoma, giant cell tumor and aneurysmal bone cyst

Preferred Biopsy Technique: A biopsy is usually performed to confirm the diagnosis.

Preferred Margin for this Tumor: Margins should be a s wide as possible without functional sacrifice

Histopathology findings:On gross examination, osteoblastomas are red to tan in color with hemorrhagic areas. The compact tissue is granular, friable and

gritty. The classic microscopic finding of osteoblastoma is irregular spicules of mineralized bone and eosinophilic osteoid rimmed

by osteoblasts. The vascular stroma is characterized by pleomorphic spindle cells. The tumor cells differentiate into osteoblasts

which make varying amounts of osteoid and woven bone. Cartilage production is a very rare finding in an osteoblastoma and

should raise the suspicion of osteosarcoma


Surgical resection by curettage, intralesional excision or en-bloc excision are all treatment options depending on the site.

Cryosurgery, radiation and chemotherapy may have a role in aggressive and surgically unresectable lesions of the spine.

Outcomes of Treatment and Prognosis:Osteoblastoma vs. Osteoid Osteoma inconsistent pain vs.persistent, nocturnal pain irregular tissue pattern vs. regular pattern >2

cm vs. < 1 cm Sporadic reports of malignant sarcomas arising in osteoblastoma have been published. In addition, multiple authors

have described a subset of these tumors that behaves in a much more locally aggressive fashion. These tumors have been found to

be larger and occur in slightly older individuals. Microscopically, these tumors may have a distinct appearance, including

epithelioid features and larger osteoblasts with abundant eosinophilic cytoplasm and vesicular nuclei. These tumors have been

variously termed "aggressive osteoblastoma" or "malignant osteoblastoma". The radiographic and pathologic features of these

tumors overlap with osteosarcoma.


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OsteochondromaIntroduction and Definition:

Osteochondroma, or osteocartilaginous exostosis, is the most common skeletal neoplasm. The cartilage capped subperiosteal

bone projection accounts for 20-50% of benign bone tumors and 10-15% of all bone tumors.Osteochondromas are most

likely caused by either a congenital defect or trauma of the perichondrium which results in the herniation of a fragment of the

epiphyseal growth plate through the periosteal bone cuff. Osteochondromas can either be flattened (sessile) or stalk-like

(exostosis) and appear in a juxta-epiphyseal location. Osteochondromas are also the result of radiation therapy in children.

After the close of the growth plate in late adolescence there is normally no further growth of the osteochondroma.


The lesions occur only in bones that develop from cartilage (endochondral ossification). Osteochondromas are found most

often in long bones, especially the distal femur and proximal tibia, with 40% of the tumors occurring around the knee.

Osteochondromas occur most frequently in the first two decades of life with a ratio of male to female of 1.5 to 1.

Symptoms and Presentation:Clinically, osteochondromas present with pain due to mechanical irritation or a painless mass. A fracture can occur through

the stalk of the lesion which also causes pain.

X-Ray Appearance and Advanced Imaging Findings:Plain films are normally enough to diagnose osteochondromas. Sessile lesions cover a wide area and as a result cause

metaphyseal widening or a "trumpet shaped deformity" on x-ray. Lesions with stalks are often found more distally and are

common over the posterior femoral metaphysis. CT is helpful in determining if the marrow and cortices of the lesion are

continuous with the bone. The relationship of the lesion to other structures and the thickness of the cartilage cap are bestdelineated with MRI.




Histopathology findings:On gross examination, an osteochondroma is an irregular bony mass with a bluish gray cap of cartilage. Opaque yellow

cartilage has calcification within the matrix. The base of the lesion has a rim of cortical bone and central cancellous bone.

Occasionally, a bursae develops over an osteochondroma. Normally, the cartilage cap ranges from 1-6 mm thick. Over 2 cm

of cartilage or renewed growth of a dormant lesion are signs of possible malignant transformation.Under the microscope, an

osteochondroma has endochondral ossification on the basal surface of hyaline cartilage so it resembles a normal growth plate

with rows of chondrocytes. The cartilage is more disorganized than normal, has binucleate chondrocytes in lacunae, and iscovered with a thin layer of periosteum

Treatment Options for this Tumor:There is no treatment necessary for asymptomatic osteochondromas. If the lesion is causing pain or neurologic symptoms due

to compression it should be excised at the base.

Outcomes of Treatment and Prognosis:As long as the entire cartilage cap is removed there should be no recurrence. Patients with many especially large

osteochondromas should have regular screening exams and radiographs to detect malignant transformation early.


Hereditary multiple osteochondromatosis is an autosomal dominant condition that can lead to both sessile and pedunculated

lesions. The lesions may occur on different bones or on the same bone, and symptoms present in the first decade of life. Therisk of malignant transformation to chondrosarcoma in hereditary multiple osteochondromatosis is unknown, but may be 25-

30% compared to approximately 1% for a solitary osteochondromas.3 The risk of malignant degeneration increases as the

number and size of the osteochondromas increases. In general, a sessile lesion is more likely to degenerate into sarcoma than

an exostosis


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OsteoidOsteomaIntroduction and Definition:

Osteoid Osteoma is a benign bone lesion with a nidus of less than 2 cm surrounded by a zone of reactive bone. This lesion accounts

for approximately 10 % of benign bone tumors. Approximately 11% of these painful, benign tumors occur in the bones of the foot.

The neck of the talus is the most common location.

Incidence and Demographics: The tumor occurs most frequently in the second decade, with a peak age in the early twenties,and

affects males twice as often as females. Osteoid Osteoma is found in the diaphysis or the metaphysis of the proximal end of the bone

more often than the distal end.

Symptoms and Presentation:Osteoid osteoma has a distinct clinical picture of dull pain that is worse at night and disappears within 20 to 30 minutes of treatment

with non-steroidal anti-inflammatory medication. Joint pain may be present with a periarticular lesion and synovitis can occur

secondary to an intraarticular lesion. Local symptoms can include an increase in skin temperature, increased sweating and tenderness

Epiphyseal lesions can cause abnormal growth.


The classic radiological presentation of an osteoid osteoma is a radiolucent nidus surrounded by a dramatic reactive sclerosis in the

cortex of the bone. The center can range from partially mineralized to osteolytic to entirely calcified. The sclerotic bone surrounding

the nidus can be minimal when the tumor involves a small bone. The lesion can occur only in the cortex, in both the cortex and

medulla, or only the medulla. The reactive sclerosis may be present or absent. Bone scan shows a small, very intense focus of

abnormal uptake. CT is the preferred method of evaluation, especially if the lesion is in the spine or obscured by reactive sclerosis.

The four diagnostic features include:

(1) sharp round or oval lesion(2) less than 2 cm in diameter (if the nidus is larger than 2 cm, the diagnosis of osteoid osteoma is excluded)

(3) has a homogeneous dense center

(4) has a 1-2 mm peripheral radiolucent zone

Differential Diagnosis: osteoblastoma, osteomyelitis, arthritis, stress fracture and enostosis




On gross examination, osteoid osteoma is a brownish-red, mottled and gritty lesion that is distinct from the surrounding bone. It can be

present in the cortex or medullary canal. Osteoclasts are present. The nidus is surrounded by sclerotic bone with thickened trabeculae

Microscopically, the nidus consists of a combination of osteoid and woven bone surrounded by osteoblasts. The oval shaped nidus is

welvascularized and clearly separate from the reactive woven or lamellar bone.


In most cases, nonsteroidal anti-inflammatory medicines give substantial relief, and any history of taking these medicines should be

carefully reviewed. If there is absolutely no relief of pain from taking NSAIDs, the diagnosis of osteoid osteoma is less likely. Lesion

adjacent to a joint may cause ankylosis or mimic a pauciarticular inflammatory arthritis, such as Reiter's disease. The local swelling

erythema and tenderness can mimic infection. When there is significant involvement of a nearby joint, the relief from nonsteroidal

medicines can be less dramatic. Patients who respond well to NSAIDs and aspirin may be successfully treated with these medications

until the lesion disappears. The average time to resolution is 22 months. Many patients will not be able to tolerate the pain this long,

and request surgical removal. For these cases, the goal is complete removal of the lesion by the least invasive means possible. For

lesions in the hindfoot and midfoot, radio thermal ablation by CT guided needle is the recommended technique. A radiofrequency

generator forms an alternating high frequency radio wave that passes from the electrode tip into the surrounding tissue, where energy

is dissipated as heat. The tissue itself is heated, not the radiofrequency probe. The high success rate combined with the extremely low

rate of complications strongly favor this technique. Radio thermal ablation can be difficult in the smaller bones because of difficulties

with targeting the lesion in the CT scanner. In addition, when the lesion is in a small bone, there is risk of damage to nearby tendons or

neurovascular structures. For superficial lesions in the forefoot, open surgery is still the preferred treatment. The surgeon needs to be

able to locate the nidus using radiographs, anatomic landmarks, and direct observation. Other techniques for locating the nidus have

been described. The surrounding reactive bone can be extremely dense, and it may also be hypervascular and somewhat porous.


It is essential to remove the entire nidus because failure to do so will lead to recurrence. Surgical removal often leads to weakening of

the affected bone, and bone grafting, plating, and prolonged nonweightbearing with activity restrictions may be necessary.


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UnicameralBoneCystIntroduction and Definition:Unicameral bone cyst (UBC), also known as simple bone cyst, is a benign lesion of uncertain origin that consists of a fluid filled

cavity lined by a thin membrane. Several etiologies have been proposed, including expansion of synovial tissue trapped in the bone

during development, local failure of ossification, or obstruction of the venous outflow of the bone. They are found in the metaphysis

of long bones, with the most common site being the proximal humerus, followed by the proximal femur. In the foot, UBC occurs

almost exclusively in the calcaneus. The location and appearance is characteristic and biopsy may not be needed to confirm the

diagnosis. The location is very specific. The lesion is in the lateral portion of the calcaneus sub-adjacent to the middle facet. The apex

of the lesion is towards the forefoot. The margin of the lesion is sharply defined, sometimes with a sclerotic rim. There is no matrix

mineralization or periosteal reaction.

Incidence and Demographics:UBC's are found most commonly in children between the ages of ages 5 to 20 years old, and the ratio of male to female is 2:1.

Symptoms and Presentation:Most UBC's are asymptomatic and only present when a pathological fracture occurs or it may presents as an incidental finding or with

mild aching pain during sports or running.


The plain film is usually enough to make a diagnosis of a UBC. The lesion appears as a well defined osteolytic area with a thin

sclerotic margin. It fills and perhaps slightly expands the juxta-epiphyseal metaphysis of the bone. The lesion is relatively symmetrica

with respect to the midline axis of the bone. The lesion is not eccentric and does not break out through the cortex or form any extra

osseous mass. There is no periosteal reaction visible unless there has been a previous fracture. A fragment of cortex that has fallen into

a dependent position inside the cyst is known as the "fallen leaf" or "fallen fragment" sign. On MRI the lesion has high signal intensitywith minimal loculations or heterogeneity consistent with a fluid filled cavity. Differentiation of UBC from other similar lesions

should be possible based on the MRI findings. Intraosseous lipoma tyopically has signal intensity consistent with adipose tissue (high

signal intensity on T1 and T2 alike) and aneurysmal bone cyst has a multiloculated appearance with fluid-fluid levels with each

loculation. On CT the lesion has no matrix, and fills the bone to a variable degree. There is no periosteal reaction. The cortex is often

quite thin. Bone scan is not recommended for these lesions

Differential Diagnosis: Intraosseous lipoma, ABCs



Histopathology findings:Microscopically, the UBC has a membrane made up of a layer of flattened or cuboidal cells that resemble endothelium. The cyst fluid

resembles synovial fluid. If a fracture has occured, there may be a hemorrhage, granulation tissue, calcifications, or giant cells whichmay confuse the diagnosis


Displaced fractures through UBC in the calcaneus are uncommon. Treatment for asymptomatic cases consists of observation and

follow-up radiographs to insure the lesion is not growing or changing. Painful cysts can be treated with a wide variety of more or less

invasive techniques and there is a lack of consensus as to the optimum choice of treatment. Minimally invasive techniques including

aspiration and injection with methylprednisolone, bone marrow, autogenous or allogenous bone graft or bone graft substitutes, or a

combination of these, or curettage without grafting, creating multiple drill holes, or percutaneous screw decompression. All of these

techniques have been shown to be effective for some cysts. Virtually all the reports in the literature, however, have a relatively low

level of evidence (level III, IV, V). New reports from a randomized, multi-center trial are due out soon, which apparently show no

significant benefit for bone matrix or bone marrow preparations over simple injections of methylprednisolone. However, the

biological mode of action of the injections remains unknown. Various technical factors have been proposed that may increase the

success rate of steroid injections, including wide spacing of the needles to ensure complete exposure of the lesion, and using

radiological dye to insure complete filling of the lesion. These techniques may decrease the need for multiple injections. The author of

this site recommends that simple treatments with minimal morbidity be tried first, and that more invasive, expensive, and risky

interventions be reserved for difficult cases.

Outcomes of Treatment and Prognosis:These lesions usually heal when the patient is skeletally mature, but a few persist into adulthood. The lesions grow in proportion to the

growth of the bone they are in. Once the bone is finished growing, the UBC should also stop growing. These lesions may recur

especially in younger children


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Foot & Ankle Bone Tumors

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