Musculoskeletal Pathology Part I Bones. Bone diseases Metabolic bone diseases Osteoporosis...
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Transcript of Musculoskeletal Pathology Part I Bones. Bone diseases Metabolic bone diseases Osteoporosis...
Musculoskeletal PathologyPart I
Bones
Bone diseases
Metabolic bone diseasesOsteoporosisOsteomalacia and ricketsFibrous osteodystrophyPaget’s disease
Fractures
InflammationsOsteomyelitisTuberculous osteomyelitis
TumoursPrimarySecondary (metastatic)
Osteoporosis
absolute decline in the bone mass (bone atrophy)
Pathogenesisexcessive amount of osteoclastic resorption or impairment of osteoblast-mediated bone formation, or both
Primary osteoporosis:
type I osteoporosis (postmenopausal): ↓oestrogen → ↑bone resorption (↑number and activity of osteoclasts)
type II osteoporosis (senile): individuals older than 70 yearsimpairment of bone formation (failure to replace resorbed bone)
Secondary osteoporosisCushing’s syndromehyperthyreoidismhypogonadism (early oophorectomy)malnutritionsubtotal gastrectomyimmobilisation, hemiplegia, paraplegiatreatment with glucocorticoids or certain anticonvulsants
Clinical features:fractures as a result of minimal trauma
hip fracturescompressive fractures of the vertebral bodies – kyphosis (“dowager’s hump“)fractures of the distal radius (Colles’ fracture)
Morphology:thinning of individual trabeculaloss of normal trabecular networkmineralisation is normal
Osteomalacia and Rickets (rachitis)
defective mineralisation of osteoid matrix
Lack of vitamin D:low dietary intakelack of sunlightsmall gut malapsorptionchronic liver and/or renal diseases (impaired hydroxylation of vitamin D precursors)
Hypophosphataemia (much less common, resistance to treatment with vitamin D):hereditary (abnormality of phosphate transport by the renal tubular epithelium)tumour-associated (effect of certain mesenchymal neoplasms)
Osteomalacia
adults with closed epiphysesnormal bone mass, but increase in amount of osteoid (more than 20% of the trabecular surface)deformities (kyphoscoliosis, contracted pelvis, limb curvature), fractures
Rickets
children (epiphyses still open and active)failure of matrix mineralisationdisturbance of endochondral ossification: very poor formation of zone of provisional calcification, marked enlargement of zone of hypertrophic cartilagedeformities: craniotabes rhachitica, caput quadratum (frontal and parietal bossing), bulging of the costochondral junctions („rickety rosary“)
Fibrous osteodystrophysevere hyperparathyreoidism (especially primary)excessive osteoclastic resorption of boneoutline of bony trabeculae shows deep indentations filled with numerous osteoclasts and connective tissue
In severe cases occur so-called brown tumors (a misnomer): areas in which trabecular bone has been completely eroded away and replaced by vascular fibrous tissue with many osteoclasts and hemosiderin depositions (brown color) – should not to be confused with true giant cell tumor uf bone
Clinical features: bone pain, pathological fractures occasionally, hypercalcaemia
Paget’s disease of bone (osteitis deformans)
chronic condition, enlargement and deformities of affected bones individuals over the age of 45 years, frequency increases with advancing ageonly one bone or many bones (polyostotic form)Sites: skull, pelvis, spineAetiology unknown, some osteoclasts contain intranuclear inclusions resembling the nucleocapsid structure of paramyxoviruses → viral infection suggested, but attempts to isolate virus failed
Macroscopic features: bones enlarged and thickened (thick calvarium) and softer (deformities – bowing of lower limbs), narrowing of the foramina of cranial nerves (neuropathies, deafness)
Microscopic features: repeated episodes of intense bone resorption and subsequent reparationOsteolytic phaseMixed or osteoblastic phaseOsteosclerotic or burned-out phase (mosaic-like appearance due to numerous cement lines)
Greater risk of developing osteosarcoma
Fracturesbreaks in the continuity of boneInfraction = incomplete fracturePathological fracture: bone altered by some previous lesion (osteoporosis, cysts, tumours), only minor trauma or spontaneously
Fracture healing:haematoma between severed ends of bone + necrosis of bone marroworganization of haematoma with granulation tissueconnection of bone ends by fibrous tissue (fibrous callus)woven bone and cartilage in fibrous tissue (provisional callus)gradual remodelling to mature lamellar bone (definite callus)
Impaired fracture healing (infection, poor immobilization, metabolic bone diseases): exuberant callus with excessive cartilage formation, sometimes non-union of bone ends (pseudo-arthrosis)
Osteomyelitisinfection-mediated inflammation of bonepus-forming organisms (staphylococci, streptococci...)
infection may penetrate bone:directly (compound fractures, operations)via the bloodstream from distant primary focus (haematogeneous osteomyelitis)
Morphologyacute pyogenic inflammation of bone marrow – rise in interstitial pressure compromises the local blood supply – ischaemic necrosis of cancellous bone
spread of inflammation to the subperiosteal space (subperiosteal abscess) – periosteal blood vessels shear off - ischaemic necrosis of cortical bone
perforation of the periosteum – spread through soft tissues and skin forming a sinus track, portions of dead bone can be discharged onto the skin
Complicationssepsis, amyloidosis, pyogenic arthritis, squamous carcinoma of the skin (after many years)
Tuberculous osteomyelitis
children, blood-borne infectionlong bones, vertebrae
bone destruction associated with granulomatous lesion with caseation
Tuberculosis of the spine (Pott’s disease): sharp anterior angulation of the spine (kyphosis), caseation may spread to the paravertebral soft tissues and track down along the psoas muscle to form an inguinal subcutaneous mass
Bone metastases
much more common than the primary bone tumoursusually multiple
Osteolytic (bone destruction)Osteoblastic (reactive bone formation)
Tumors commonly producing bone metastases: prostatic carcinoma, breast carcinoma, renal cell carcinoma, carcinoma of stomach, thyroid carcinoma
Primary bone tumoursLess common, usually solitaryFeatures of considerable diagnostic value: age of the patient, site of the lesion
Classification (simplified):Bone-forming tumoursOsteomaOsteoid osteomaOsteoblastomaOsteosarcomaCartilage-forming tumoursOsteochondromaChondromaChondrosarcomaOther tumoursGiant cell tumor of boneEwing’s sarcomaTumour-like lesionsFibrous dysplasiaBone cysts
Osteoma
benign lesiondense mature lamellar boneskull, facial bones, paranasal sinuses, orbit
Macrousually small bony outgrowth
Micromature lamellar bone
may be a component of Gardner’s colonic polyposis syndrome
Osteoid osteoma
benign osteoblastic lesionyoung people (5-24 years), male predominance
Clinical features: quite severe painlong bones (femur, tibia), ends of the shafts
Morphologysharply outlined osteolytic defect (nidus) less than 1 cm in diameter, surrounded by rim of sclerotic bonenidus composed of haphazardly oriented trabeculae of woven bone and highly vacularized fibrous stromatrabeculae lined by plump osteoblasts and rare osteoklasts
Osteoblastoma
rare, closely related to osteoid osteoma, but larger than 1cm (“giant osteoid osteoma“), and generally lacking the reactive rim of dense sclerotic bone
age similar to that of osteoid osteomaspine, small bones of the hands and feet
Microscopical appearancevery similar to osteoid osteoma (trabeculae of woven bone lined by plump osteoblasts and osteoclasts, vascularized fibrous stroma)
benign, but examples showing atypical osteoblast and a poorly demarcated edge tend to recur, although not metastasise (aggressive osteoblastoma)
Osteosarcoma
most common primary malignant neoplasm of bone
peak incidence between 10-25 years, in middle-aged and elderly people associated with Paget’s disease, predominance of males
metaphyseal region of the long bones (lower end of femur, upper end of tibia, upper end of humerus)
arises from within medullary cavity and invades the cortical bone, elevates the periosteum (Codman’s triangle) and penetrates into soft tissues
Microscopic features:bone or osteoid formation by the tumour cells (irregular „lace-like“ osteoid trabeculae surrounded by atypical malignant osteoblasts), areas of malignant cartilage and sarcomatous spindle cell stroma
highly malignant neoplasm with poor prognosis, metastases to lungs
Parosteal osteosarcoma
variant of osteosarcoma in slightly older people
juxtacortical position of metaphyseal region
large lobulated mass tending to encircle the shaft
very slow growth
well-formed bone and osteoid set in spindle cell stroma with only scanty cytological signs of malignancy
very good prognosis with adequate resection
Osteochondroma (exostosis)
very common, hamartomas rather than true neoplasms
young people, male predominance
long bones (femur, tibia, humerus), metaphyses
pedunculated or sessile lesions consisting of bone covered by a cap of cartilageordered columnar arrangement of chondrocytes and zone of endochondral ossification
Osteochondromatosis: multiple osteochondromas, some risk of malignant transformation (secondary chondrosarcoma)
Chondroma
benign tumour consisting of mature hyaline cartilage
children, adolescents and young adults, incidence equal in both sexes
medullary cavity of the small bones of the hands and feet (enchondroma)radiolucent lesion expanding and thinning cortical bone
lobules of mature hyaline cartilage, some irregularity and atypia of chondrocytes without any adverse prognostic significance
Ollier’s disease (multiple chondromas)
Chondrosarcoma
malignant cartilaginous tumour, primary (arising de novo) or secondary (malignant transformation of benign cartilaginous tumours)
middle aged and elderly (primary chondrosarcoma), younger age group (secondary chondrosarcoma), M/F ratio 3:2
central skeleton (ribs, pelvis, proximal end of femur and humerus)
aggressive growth (destruction of cortical bone, extension into the soft tissues)
high cellularity, cytologic atypia of chondrocytes, binucleated cells, mitotic activity, necrosis
Giant cell tumor of bone
third decade
long bone epiphyses
lytic and radiolucent lesion
brown with grey and red areas (fibrosis and haemorrhage)
mononuclear cells (the only neoplastic element) and multinuclear giant cells resembling osteoclasts (reactive)
locally aggressive, may recur
metastases to the lungs in about 4% of cases
Ewing’s sarcoma
primitive neuroectodermal tumour (PNET)
5-20 years, male preponderance
almost any bone, most often long bones and pelvis
lytic destruction of the bone, widening of the medullary cavity, cortical infiltration and elevation of the periosteum – “onion-skin“ or “sun-ray“ periosteal reactiongrayish white, focal necrosis and haemorrhage
sheets of small uniform round cells, droplets of glycogen in the cytoplasm of the tumor cells (PAS positive material)
very aggressive tumour with poor prognosis, metastatic spread to lungs and other bones
Fibrous dysplasia
non-neoplastic condition
children and adolescents
ribs, femur, tibia, maxilla, mandibula, humerus
monostotic and polyostotic form
well-demarcated localized area of bone replaced by the fibrous tissue containing spicules of woven bone with peculiar sickle or fish-hook shape
McCune-Albright syndrome: polyostotic FD + patchy skin pigmentation + precocious puberty
Bone cysts
Solitary bone cystunicameral cavity lined by smooth fibrous membrane
Aneurysmal bone cystmultiple spaces filled with red blood cells separated by thin fibrous septa with numerous osteoclasts