PATHOLOGY OF FIBRO OSSEOUS

LESIONS

Dr.Roohia

FD is derived from osteoprogenitor, fibroblastlike Cells Activating, somatic mutation in the GNAS1 gene found on

chromosome 20q13.

2 distinct missense mutations in the alpha subunit of a G stimulatory protein have been identified that account for disease processes.

activation of adenylyl cyclase

cyclic adenosine monophosphate. alteration in the transcription and expression of several downstream target genes, including c-fos, a proto-oncogene

FD

“Arrest of bone maturation in woven bone with

ossification resulting from metaplasia of a nonspecific fibro-osseous type“

FD can occur in both types of bones, endochondral and membranous.

FD involves maxillary bone,also as the zygoma, sphenoid, temporal, orbital, nasal, frontal, and occipital bones.

Involvement of facial and cranial bones in FD occurs in nearly 50% of patients with the polyostotic form and in 10-27% of patients with MFD.

<1% malignant tranformation.

First or second decades of life. slow-growing, painless expansion of the bone. Facial asymmetry may be apparent. Visual disturbances, proptosis, orbital

dystopia, nasal malfunction, dental problems and sensory disturbances in the affected regions. 

FD

Extraosseous Manifestations: McCune-Albright syndrome (MAS): polyostotic FD, skin hyperpigmentation (café au lait spots), multiple endocrinopathies - gonadal hyperfunction - sexual precocity (especially in females). hyperthyroidism, adenomas of various endocrine glands including the pituitary

gland, Cushing syndrome, acromegaly, benign ovarian cysts, linear epidermal nevi, and Neonatal cholestasis. The skin spots often are unilateral and ipsilateral to the FD

lesions .

Fibrous dysplasia

Mazabraud syndrome: polyostotic FD and intramuscular myxomas

FD

Osteoma is the most common tumor of the paranasal sinuses. male predominance. Etiology:3 theories Developmental theory: apposition of membranous and endochondral tissues traps

some of these embryonic cells, eventually leading to unchecked osseous proliferation.

Traumatic theory: inflammatory process as the inciting force for bony tumor

formation. Infectious theory: infectious theory suggests that osteitis resulting from chronic

infection is to blame.

surface of an osteoma is

smooth and lobulated H/E:3 types Eburnated type- ivory or

compact type, is very dense and lacks haversian canals.

The mature type- or osteoma spongiosum, is composed of softer bone more similar to cancellous bone.

The mixed type of osteoma contains elements of both the eburnated and mature forms

Fibrous dysplasia Early FD usually exhibits

a moderately cellular, fibrous stroma containing haphazardly arranged, uniform, spindle-shaped to ovoid fibroblasts. variable number of small, ovoid blood vessels are seen within the stroma, and collagen bundles often are scant.

FD

Scattered, irregularly shaped trabeculae of woven bone are seen throughout the stroma.

Delicate and curvilinear and have been likened to Chinese scrip-writing.

The lesional bone fuses with the adjacent uninvolved bone.

Focally scattered, small, ovoid calcifications also may be seen.

Artifactual separation of the lesional bone from the surrounding stroma

Cherubism formerly was described as familial

fibrous dysplasia. Cherubism is a rare, autosomal dominant, self-

limiting disorder that exhibits 100% male and 50% to 70% female penetrance.

Clinical manifestations of cherubism are restricted to the jawbones.

Mutations in the SH3BP2 gene, found on chromosome 4p16, have been identified

CHERUBISM

identified during early childhood. Patients typically have painless,

bilateral, symmetric jaw enlargement resulting in marked facial expansion.

continues until puberty, after which the lesions tend to undergo spontaneous resolution.

Diffuse involvement of the maxilla also may occur.If so, the midface may become expanded, resulting in exposure of the inferior portion of the sclerae. As a result, the patient’s eyes may appear to be looking upward.

numerous fibroblasts

, extravasated RBCs ,and multinucleate giant cells .

OSSIFYING FIBROMA

OFs are considered to be true benign fibro-osseous neoplasms that develop mainly within the jawbones.

third and fourth decades of life.

small asymptomatic lesions, slow-growing, expanding lesions that often average more than 3 cm in diameter at the time of diagnosis.

balanced translocations with recurring

breakpoints at Xq26 and 2q33. OF is a well-circumscribed, occasionally

encapsulated mass that may show a variety of different microscopic patterns.

moderately cellular, relatively

avascular, dense fibrous stroma. cells appear spindle-shaped to

ovoid and may be haphazardly arranged or organized in a vague storiform pattern.

The nuclei are bland appearing and contain single, inconspicuous nucleoli.

calcified material may consist of thin, irregularly shaped trabeculae of woven bone;

scattered trabeculae of lamellar bone; deposits of basophilic staining, round or ovoid, cellular or acellular calcified deposits that have been likened to cementum.

Owing to the

presence of the calcified spherules,“cemento-ossifying fibroma” or “cementifying fibroma.”

the lesional bone in OFs does not fuse to adjacent uninvolved cortical bone

Hyperparathyroidism–jaw tumor syndrome is an

autosomal dominant disease.charactarised as OF.

Adenoma induced,primry hyperparathyroidism and well-circumscribed BFOLs of the jawbones.

renal anomalies- -renal hamartomas,-polycystic kidney disease, -multiple degenerative cysts

Juvenile ossifying fibroma

Trabecular variant (TJOF) Psammomatoid variant (PJOF) the first and second decades of

life. 75% of PJOFs develop in the

orbit, paranasal sinuses, and calvaria,

Whereas 25% of all cases involve the maxilla or mandible.

95% of the documented cases of TJOF have developed within the jawbones, with maxillary lesions occurring more frequently.

Occasionally of TJOF have arisen within the fronto-ethmoid complex and sinonasal bones.

unencapsulated lesion

composed of a cell-rich stroma, usually with little collagen.

Reactive bone may be seen at the periphery of the lesion, but the lesional tissue often is seen infiltrating the surrounding normal bone.

cells are spindle-shaped to ovoid, contain bland-appearing nuclei and inconspicuous nucleoli, and may be arranged in a storiform pattern.

Focally scattered, typical mitotic figures may be seen.

TJOF, delicate “seams” of

osteoid rimmed by osteoblasts seem to arise from within the stroma.3 Plump, eosinophilic osteoblasts often are incorporated within the osteoid. Scattered, irregularly shaped trabeculae of woven bone and occasional calcified spherules also are seen.

PJOF usually are basophilic, acellular, and round or ovoid and may resemble psammoma bodies.

The term dysplasia refers to the abnormal

production and disordered development of bone and cementum-like material.

3 nonhereditary subtypes –periapical osseous dysplasia.- focal osseous dysplasia.- florid osseous dysplasia.

Osseous dysplasia

Periapical Osseous Dysplasia: Periapical osseous dysplasia is almost always

asymptomatic and nonexpanding. found in intimate association with the root apices of

the mandibular anterior teeth. Focal Osseous Dysplasia: asymptomatic, manifesting most commonly as a

small, solitary, relatively well-demarcated lesion in the posterior mandible, either in close association with the apices of teeth or in areas where a tooth has been extracted previously.

Florid Osseous Dysplasia: an innocuous, self-limiting disease. involves the posterior regions of the mandible,

manifesting as bilateral, relatively symmetrical lesions.

simultaneous, bilateral involvement of both jaws is very common.

dull, intermittent, poorly localized pain, especially in lesions that are infected secondarily.

hypercellular, fibrous

connective tissue containing numerous small, round or ovoid, vascular channels.

Numerous irregularly

shaped trabeculae of woven bone embedded within a fibrous stroma containing numerous small blood vessels .

Round, cementum-

like calcifications

Large aggregate of

acellular bone that has coalesced in a patient with florid osseous dysplasia.

Familial Gigantiform Cementoma

Another autosomal dominant disorder that is characterized by florid osseous dysplasia–like lesions of the jawbones.

no sex, age, or racial predilection for FGC.76,77 Lesions often manifest at an early age and may cause substantial rapid bony expansion and facial asymmetry.

polyostotic benign fibro-osseous disease

 trabeculae of

immature bone and irregular basophilic cemental masses in a moderately cellular fibrous connective tissue stroma

Disease Processes That May Be Included in the Differential

Diagnosis of a Benign Fibro-osseous Lesion Paget disease of bone Low-grade osteosarcoma Osteoblastoma Osteoid osteoma Cementoblastoma Central odontogenic fibroma Proliferative periostitis Renal osteodystrophy Central giant cell granuloma Brown tumor Aneurysmal bone cyst Cherubism

Pagets disease

PDB may be a monostotic or a polyostotic disease.

The maxilla is involved more commonly than the mandible.

Associated nasal obstruction and sinus obliteration also are typically seen.

A fibro-osseous pattern typically is seen. However, prominent basophilic reversal lines usually are observed within many of the bony trabeculae

Central Giant Cell Granuloma

CGCGs may develop within the maxilla, most cases manifest within the mandible.

 hypervascular, hypercellular, collagenous stroma exhibiting a variable number of osteoclast-like multinucleated giant cells.

stromal cells are bland appearing and spindle-shaped to

ovoid and often are arranged in a haphazard manner

Bone lesions develop in an estimated 10% to

15% of patients with hyperparathyroidism

Brown Tumor (Hyperparathyroidi

sm)

Aneurysmal Bone Cyst About 10% of ABCs develop in

the maxillofacial bones. association with FD, OF, JOF,

osteoblastoma, and osteosarcoma.

overlap between ABCs and CGCGs.3,129,134 The

only significant difference is that

ABCs exhibit numerous large, blood-filled, sinusoidal spaces that are surrounded by multinucleated giant cells.

Extravasated hemorrhage and hemosiderin deposits also are seen.

Thank you