Bone and cartilage Flashcards
Bone lesion with blood filled cystic spaces separated by cellular septa which contain spindle cells, osteoclast type giant cells and woven bone. Mitotic activity can be present, but there should not be atypia.
Aneurysmal bone cyst
Differential diagnosis:
Giant cell tumour of bone
Central giant cell granuloma (in jaw)
Telangiectatic osteosarcoma
Cystic change in fibrous dysplasia / non-ossifying fibroma
Plan:
Correlate with clinical history and radiology (?multiloculated cyst with fluid levels)
Examine further blocks (e.g for size, margins, areas of differing morphology)
IPX to discount DDx: H3G34W
Molecular: FISH/NGS for USP6 rearrangement
Bone lesion with bland fibrous spindle cells in which there are thin trabeculae of woven bone. Bone trabeculae have curved irregular shapes, resembling ‘letters of the alphabet,’ and lack osteoblastic rimming.
Fibrous Dysplasia
Differential diagnosis:
Osteofibrous dysplasia (if osteoblastic rimming)
Parosteal osteosarcoma
Plan:
Correlate with clinical history and radiology (?ground glass lytic lesion)
IPX to support Dx: Not required
Molecular to discount DDx: FISH for MDM2 amplification
Joint lesion with black metallic fragments or polarizable foreign material associated with histiocytes and giant cells
Detritic synovitis
Plan:
Correlate with clinical history and radiology (?previous joint replacement)
Examine under polarised light
No specific action required for this benign diagnosis
Aggregates of acellular, amorphous, pale eosinophilic material surrounded by granulomatous inflammation. May have some residual brown and needle shaped crystals, but may have been dissolved by aqueous solution.
Gout
Plan:
Correlate with clinical history and radiology (?urate levels ?joint aspiration)
Correlate with any concurrent pathology investigations (e.g. crystal analysis)
Examine under polarised light
No specific action required for this benign diagnosis
Aggregates of basophilic, rhomboid shaped crystals, surrounded by chronic / granulomatous inflammation.
Pseudogout
Differential diagnosis:
Calcinosis cutis
Plan:
Correlate with clinical history and radiology (?joint aspiration)
Correlate with any concurrent pathology investigations (e.g. crystal analysis)
Examine under polarised light (expect positive birefringence in pseudogout)
No specific action required for this benign diagnosis
Joint / tendon lesion with a mixture of osteoclast type multinucleated giant cells, foamy macrophages, and two types of mononuclear cells - small histiocyte-like cells with pale cytoplasm and round or reniform nuclei, and larger cells with amphophilic cytoplasm (often with hemosiderin granules) and rounded vesicular nuclei.
Tenosynovial giant cell tumour
Differential diagnosis:
Giant cell tumour of bone
Plan:
Correlate with clinical history / radiology (?inside joint vs nodule on tendon vs bone tumour)
IPX to support Dx: CD68
IPX to discount DDx: H3G34W
Molecular (not required for diagnosis): CSF1 rearrangement
Articular surface of bone with coagulative necrosis of marrow and of osteocytes in bone lacunae, surrounded by rim of granulation tissue that progresses into reactive bone. Reactive bone surrounds necrotic trabeculae (‘creeping substitution’)
Avascular necrosis of the femoral head
Plan:
Correlate with clinical history and radiology
No further action required for this benign diagnosis
Cartilage with increased cellularity and nuclear atypia, areas of myxoid degeneration. Permeation of marrow space, surrounding and entrapping mature trabeculae, and can show erosion of cortex.
Chondrosarcoma
Differential diagnosis
Osteosarcoma (chondroblastic type)
Chordoma
Plan:
Correlate with clinical history and radiology (?axial skeleton location)
Examine further blocks (e.g. for size, relation to margins, areas of osteoid to suggest osteosarcoma)
IPX to discount DDx: Brachyury
Next steps: Synoptic report, discuss at MDT
Bone tumour with production of malignant osteoid (lace-like disorganized woven bone intimately associated with neoplastic cells). Can also show areas of chondroblastic (high grade cartilage) and fibroblastic appearance (atypical spindle cells with extracellular collagen).
Osteosarcoma
Plan:
Correlate with clinical history and radiology (?infiltrative mass in long bone ?aggressive periosteal reaction)
Examine further blocks (e.g. for total size, relation to margins, areas of differing morphology)
Next steps: Synoptic report, discuss at MDT
Bone tumour with a mixture of mononuclear cells (which can have mitoses, but lack significant atypia), and osteoclast-like giant cells, whose nuclei are identical in appearance to the mononuclear cells.
Giant cell tumour of bone
Differential diagnosis:
Non-ossifying fibroma
Aneurysmal bone cyst
Plan:
Correlate with clinical history and radiology (?lytic lesion at end of long bone)
Examine further blocks (e.g. for size, relation to margins, areas of differing morphology)
IPX to support Dx: H3G34W
Molecular to discount DDx: USP6 rearrangement
Next steps: Synoptic report, discuss at MDT
Spinal tumour divided into lobules by fibrous septa. Tumour cells are arranged in cords or ribbons set within a myxoid matrix, and are large with clear to eosinophilic vacuolated (bubbly) cytoplasm; these are described as ‘physaliphorous cells’.
Chordoma
Plan:
Correlate with clinical history and radiology (?clivus or sacral tumour)
Examine further blocks (e.g. for size, relation to margins, area of dedifferentiation)
IPX to support Dx: AE1/AE3, S100, brachyury
Next steps: Synoptic report, discuss at MDT
Well defined sclerotic nidus of woven bone (osteoid without lamellation) rimmed by prominent benign osteoblasts. The osteoblasts are plump and amphophilic, but not atypical.
Osteoid osteoma
Differential diagnosis
Osteoblastoma (if >1.5cm)
Plan:
Correlate with clinical history and radiology (?size of lesion ?nocturnal pain relieved by NSAID ?radiolucent nidus surrounded by sclerotic rim)
IPX to support Dx: Not required
No specific further action required for this benign diagnosis
Bone lesion with eosinophilic chondroid matrix containing osteoclast type giant cells and plump cells ringed by ‘chicken-wire’ calcification
Chondroblastoma
Plan:
Correlate with clinical history and radiology
No specific action required for this benign diagnosis
Bone lesion with bony stalk in continuity with the main marrow space, capped by mature hyaline cartilage
Osteochondroma
Plan:
Correlate with clinical history and radiology
Advice to clinician: Can be sporadic or occur in the setting of multiple hereditary exostoses. Clinical correlation is required
Joint lesion with mature adipose tissue within synovium
Synovial lipomatosis
Plan:
Correlate with clinical history and radiology
No specific action required for this benign diagnosis
Joint lesion with mature cartilage within synovium
Synovial chondromatosis
Plan:
Correlate with clinical history and radiology
Advice to clinician: Benign, but can recur or rarely undergo malignant transformation
