Pathology
Bone and Soft Tissue
Bone and soft tissue pathology for MBBS and NEET-PG: osteomyelitis, osteosarcoma, Ewing sarcoma, giant cell tumour, Paget disease and rheumatoid arthritis, mapped to NMC codes PA33.1 to PA33.5.
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Bone and Soft Tissue
Bone and soft tissue pathology for MBBS and NEET-PG: osteomyelitis, osteosarcoma, Ewing sarcoma, giant cell tumour, Paget disease and rheumatoid arthritis, mapped to NMC codes PA33.1 to PA33.5.
This chapter covers pathology of bone and soft tissue. It includes osteomyelitis, primary bone tumours and their radiological features, soft tissue tumours, metastatic bone disease, Paget disease of bone and rheumatoid arthritis.
High-yield: Bone and Soft Tissue
- Acute osteomyelitis is most often caused by Staphylococcus aureus and reaches bone by the haematogenous route in children.
- A sequestrum is dead bone, and an involucrum is the new reactive bone that surrounds it in chronic osteomyelitis.
- Tuberculous osteomyelitis of the spine is called Pott disease and can produce a cold abscess and gibbus deformity.
- Osteosarcoma is the most common primary malignant bone tumour, arising near the knee in adolescents.
- Osteosarcoma shows a Codman triangle and a sunburst pattern on radiographs due to reactive periosteal bone.
- Ewing sarcoma is a small round blue cell tumour of children with an onion-skin periosteal reaction and a t(11;22) translocation.
- Giant cell tumour of bone is a locally aggressive tumour of the epiphysis with a soap-bubble appearance.
- Osteochondroma is the most common benign bone tumour and forms a bony outgrowth capped by cartilage.
- Chondrosarcoma arises in older adults and produces a cartilaginous matrix with popcorn calcification.
- Bone metastases are far more common than primary bone tumours and are usually lytic, though prostate metastases are sclerotic.
- Paget disease of bone shows a disordered mosaic pattern of lamellar bone and a markedly raised alkaline phosphatase.
- Paget disease can be complicated by high-output cardiac failure and by osteosarcoma.
- Rheumatoid arthritis is a symmetrical inflammatory polyarthritis with pannus formation and a positive rheumatoid factor.
- Rheumatoid arthritis shows rheumatoid nodules and is associated with anti-cyclic citrullinated peptide antibodies.
Key bone tumours
- **Osteosarcoma:** Adolescents, near the knee; Codman triangle and sunburst pattern.
- **Ewing sarcoma:** Children; small round blue cells; onion-skin reaction; t(11;22).
- **Giant cell tumour:** Epiphysis; soap-bubble appearance; locally aggressive.
- **Metastases:** Commonest bone tumours; usually lytic, sclerotic in prostate cancer.
NMC competencies in this chapter
- **PA33.1:** Aetiology, pathogenesis and features of osteomyelitis
- **PA33.2:** Classification, pathology and metastases of bone tumours
- **PA33.3:** Classification, pathology and metastases of soft tissue tumours
- **PA33.4:** Aetiology, pathogenesis and complications of Paget disease of bone
- **PA33.5:** Aetiology, immunology, diagnostic criteria and features of rheumatoid arthritis
Frequently Asked Questions
What is the most common primary malignant bone tumour?
Osteosarcoma, which typically arises near the knee in adolescents and shows a Codman triangle and sunburst pattern on radiographs.
What is the difference between a sequestrum and an involucrum?
A sequestrum is a fragment of dead bone, while an involucrum is the new reactive bone that forms around it in chronic osteomyelitis.
What are the features of Ewing sarcoma?
A small round blue cell tumour of children with an onion-skin periosteal reaction and a t(11;22) translocation.
How does rheumatoid arthritis affect joints?
It causes a symmetrical inflammatory polyarthritis with pannus formation, joint destruction and a positive rheumatoid factor.
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