Bone and Soft Tissue for NEET PG Pathology: Osteomyelitis, Bone Tumours, Paget Disease, Rheumatoid Arthritis, Osteoarthritis, Gout, Sarcoma

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🎯 Exam priority: Medium–high. Expect: bone tumour by age and site (epiphysis vs metaphysis), Codman triangle and onion-skin periosteum, Ewing translocation, osteomyelitis organisms and sites, Paget disease markers and sarcoma risk, RA vs OA joints, gout vs CPPD crystals, and soft tissue sarcoma translocations.

CBME mapping: PA 32.1–32.7. Rickets and osteomalacia are in article 8; myeloma in article 13; translocations in article 4.

Bone tumours, infection, Paget disease, joints and soft tissue sarcoma. Drawn by TrackNation.

Osteomyelitis and Paget Disease

• Osteomyelitis: about 80% from contiguous spread (wounds, nearby infection), often polymicrobial; the rest blood-borne or from open fractures and surgery. S. aureus is present in at least half. Blood-borne disease in children hits the metaphyses of tibia, femur or humerus; in adults it hits the vertebrae. Adult risks: age, haemodialysis, sickle cell disease, catheters, immunosuppression, injection drug use. Dead bone = sequestrum.

• Paget disease of bone: late-onset, localised, accelerated bone turnover (overactive osteoclasts, NF-κB; SQSTM1 variants) replacing normal matrix with soft, enlarged bone. Pelvis, femur and skull most often. Raised alkaline phosphatase; skull X-ray shows a mosaic of sclerosis and lucency. New or severe pain suggests osteosarcoma.

Bone Tumours

• Metastases far outnumber primary malignant bone tumours in adults — from breast, lung, prostate, kidney, thyroid and colon.

• Osteochondroma (exostosis): the commonest benign bone tumour; ages 10–20; near the ends of long bones; multiple ones = multiple hereditary exostoses (autosomal dominant).

• Giant cell tumour: 20s–30s; epiphyseal (and distal metaphyseal-epiphyseal); locally aggressive. Osteoid osteoma: radiolucent nidus with central calcification. Aneurysmal bone cyst: expansile, usually before 25.

• Osteosarcoma: the commonest primary malignant bone tumour (counting myeloma as marrow). Peaks in adolescence (growth spurt) and after 60 (Paget, bone infarcts, prior radiation). Malignant osteoid; around the knee (distal femur > proximal tibia), metaphyseal-diaphyseal; Codman triangle; spreads to lung or other bone.

• Ewing sarcoma: small round blue cell tumour, peak 10–20 years, mostly extremities; layered periosteal new bone gives an onion-skin look; EWSR1-FLI1 fusion from t(11;22) in about 85%.

• Chondrosarcoma: malignant cartilage-forming tumour; mostly primary, sometimes arising from an enchondroma or osteochondroma (Ollier disease, Maffucci syndrome, multiple hereditary exostoses).

Joints

• Rheumatoid arthritis: autoimmune synovitis; genetic link to the HLA-DRB1 shared epitope; smoking may contribute. Hyperplastic synovium (pannus) erodes cartilage and bone. RF and anti-CCP antibodies. Spares DIP joints. Rheumatoid nodules (granulomas) in up to 30%.

• Osteoarthritis: progressive cartilage loss with osteophytes and sclerosis; pain on use; morning stiffness under 30 minutes; non-inflammatory fluid. Heberden (DIP) and Bouchard (PIP) nodes.

• Gout: monosodium urate crystals; first attack usually one joint, often the first MTP; urate > 6.8 mg/dL; needle-shaped birefringent crystals; tophi with a granulomatous rim. CPPD: positively birefringent crystals; chondrocalcinosis, commoner with age.

Soft Tissue Sarcoma

• Adult sites: extremities 45%, intra-abdominal 38%, trunk 10%, head and neck 5%.

• Syndromes: Li-Fraumeni (TP53), neurofibromatosis 1 (NF1), Gardner (APC).

• Signature translocations: synovial sarcoma t(X;18); myxoid liposarcoma t(12;16). Undifferentiated pleomorphic sarcoma was formerly called malignant fibrous histiocytoma. Synovial, clear cell, angiosarcoma, rhabdomyosarcoma and epithelioid sarcoma tend to reach lymph nodes.

Traps the Examiner Sets

• Epiphysis in a 20–30-year-old = giant cell tumour; metaphysis around the knee in a teenager = osteosarcoma.

• Onion skin = Ewing; Codman triangle = osteosarcoma.

• Child osteomyelitis = metaphysis; adult blood-borne = vertebra.

• RA spares DIP; OA loves DIP (Heberden).

• Gout = needles; CPPD = positively birefringent.

Memory Hooks & Shortcuts

Shortcuts to lock in this article's numbers and lists. Each one only re-packages facts proven above.

• 🧠 Giant cell tumour = Grown-ups' Epiphysis (20–30s) — GCT

• 🧠 Ewing = Eleven-Twenty-two, onion skin — Ewing sarcoma

• 🧠 Osteosarcoma = Osteoid + Codman + Knee — osteosarcoma

• 🧠 Paget = Pelvis, Femur, Skull + ALP — Paget disease

• 🧠 Gout Needles, CPPD Positive — crystals

• 🧠 Synovial = X and 18 (Xtra-eighteen) — synovial sarcoma

Rapid-Revision Cards

• Osteomyelitis organism

  S. aureus ≥ 50%.

• Osteomyelitis route

  Contiguous ~80%; blood-borne rest.

• Child vs adult site

  Child metaphysis; adult vertebra.

• Sequestrum

  Dead bone.

• Osteochondroma

  Commonest benign; 10–20 y; MHE.

• Giant cell tumour

  20s–30s; epiphysis; locally aggressive.

• Osteoid osteoma

  Radiolucent nidus, central calcification.

• Osteosarcoma

  Teens + > 60; knee; osteoid; Codman; lung mets.

• Ewing

  10–20 y; small round blue cells; onion skin; t(11;22).

• Chondrosarcoma

  Cartilage; from enchondroma/osteochondroma.

• Bone metastases

  Commonest in adults; breast, lung, prostate.

• Paget of bone

  Osteoclasts; ALP ↑; mosaic; sarcoma risk.

• RA

  Pannus; RF, anti-CCP; HLA-DRB1; spares DIP.

• RA nodules

  Up to 30%.

• OA

  Cartilage loss; osteophytes; Heberden/Bouchard.

• Gout

  Needle urate crystals; first MTP; tophi.

• CPPD

  Positively birefringent; chondrocalcinosis.

• Synovial sarcoma

  t(X;18).

• Myxoid liposarcoma

  t(12;16).

• Sarcoma syndromes

  Li-Fraumeni, NF1, Gardner.

Sources

Facts in this article were checked against these documents.

• MSD Manual Professional: Osteomyelitis; Benign Bone Tumors and Cysts; Primary Malignant Bone Tumors; Metastatic Bone Tumors; Paget Disease of Bone — Merck & Co. (MSD Manuals), reviewed 2025–26 (link)

• MSD Manual Professional: Rheumatoid Arthritis; Osteoarthritis; Gout; Calcium Pyrophosphate Arthritis — Merck & Co. (MSD Manuals), reviewed 2025–26 (link)

• PDQ Adult Soft Tissue Sarcoma Treatment (Health Professional Version) — US National Cancer Institute, 2026 (link)

• Competency Based Undergraduate Curriculum, Pathology (PA 32) — National Medical Commission, 2024

Test Yourself: Practice Questions

Thirty questions in NEET PG style, most of them clinical vignettes.

Practice Questions (NEET PG pattern)

Original questions written in the style of the exam: +4 for a correct answer, −1 for a wrong one. Every answer was checked against the sources listed above. NEET PG papers are not published by NBEMS, so these are not past-paper questions.

Q1. The organism present in at least half of osteomyelitis cases is

• (a) Staphylococcus aureus

• (b) Pseudomonas

• (c) Salmonella

• (d) Mycobacterium tuberculosis

Q2. In a child, blood-borne osteomyelitis most often affects the

• (a) skull

• (b) epiphysis only

• (c) vertebral body

• (d) metaphysis of a long bone such as the tibia or femur

Q3. A haemodialysis patient develops blood-borne osteomyelitis. The usual site in adults is the

• (a) distal femoral metaphysis

• (b) phalanges

• (c) vertebrae

• (d) skull

Q4. A fragment of dead bone within an area of chronic osteomyelitis is called

• (a) a sequestrum

• (b) a Brodie abscess

• (c) a tophus

• (d) an involucrum

Q5. Most osteomyelitis arises by

• (a) blood-borne spread (~80%)

• (b) lymphatic spread

• (c) contiguous spread from nearby infected tissue or wounds (~80%)

• (d) spread along nerves

Q6. A 15-year-old has a lump near the end of a long bone; X-ray shows an osteocartilaginous exostosis. The lesion and its status are

• (a) osteosarcoma — malignant

• (b) osteochondroma — the commonest benign bone tumour

• (c) giant cell tumour — epiphyseal

• (d) Ewing sarcoma

Q7. A 28-year-old has a locally aggressive lesion in the epiphysis of a long bone. The likely tumour is

• (a) osteosarcoma

• (b) giant cell tumour of bone

• (c) Ewing sarcoma

• (d) osteochondroma

Q8. CT of a painful small bone lesion shows a radiolucent nidus with central calcification. The diagnosis is

• (a) enchondroma

• (b) osteochondroma

• (c) aneurysmal bone cyst

• (d) osteoid osteoma

Q9. Multiple osteochondromas inherited in an autosomal dominant pattern are called

• (a) multiple hereditary exostoses

• (b) Maffucci syndrome

• (c) Ollier disease

• (d) fibrous dysplasia

Q10. A 16-year-old has pain and swelling above the knee; X-ray shows a destructive distal femoral lesion with a Codman triangle. Biopsy will show

• (a) small round blue cells with t(11;22)

• (b) malignant cells producing osteoid

• (c) giant cells in an epiphyseal lesion

• (d) cartilage only

Q11. The second age peak of osteosarcoma, after 60, is linked to

• (a) gout

• (b) multiple hereditary exostoses only

• (c) Paget disease, bone infarcts and prior radiation

• (d) rickets

Q12. Osteosarcoma most commonly metastasises to the

• (a) liver

• (b) lungs (and other bones)

• (c) lymph nodes first

• (d) brain

Q13. A 13-year-old has a long-bone tumour with layered 'onion-skin' periosteal reaction; biopsy shows small round blue cells. The typical genetic change is

• (a) t(11;22) producing EWSR1-FLI1

• (b) t(12;16)

• (c) t(X;18)

• (d) BRAF V600E

Q14. The peak age of Ewing sarcoma is

• (a) 10–20 years

• (b) 40–60 years

• (c) under 2 years

• (d) over 70 years

Q15. A malignant cartilage-forming bone tumour that may arise from a pre-existing enchondroma is

• (a) osteosarcoma

• (b) chordoma

• (c) Ewing sarcoma

• (d) chondrosarcoma

Q16. In adults, the commonest malignant tumour found in bone is

• (a) Ewing sarcoma

• (b) osteosarcoma

• (c) metastatic carcinoma

• (d) chondrosarcoma

Q17. An older man has an enlarging skull and bone pain; alkaline phosphatase is high and skull X-ray shows a mosaic of sclerosis and lucency. The disease is

• (a) Paget disease of bone

• (b) multiple myeloma

• (c) osteoporosis

• (d) osteomalacia

Q18. In Paget disease of bone, new severe pain at a pagetic site should raise suspicion of

• (a) osteoid osteoma

• (b) gout

• (c) septic arthritis

• (d) osteosarcoma

Q19. The cell whose overactivity drives Paget disease of bone is the

• (a) chondrocyte

• (b) osteocyte

• (c) plasma cell

• (d) osteoclast

Q20. A woman has symmetrical small-joint polyarthritis sparing the distal interphalangeal joints; anti-CCP is positive. The destructive tissue in her joints is

• (a) osteophytes

• (b) urate tophi

• (c) hyperplastic synovium (pannus)

• (d) calcium pyrophosphate deposits

Q21. The genetic predisposition to rheumatoid arthritis maps to

• (a) a shared epitope in HLA-DRB1

• (b) HLA-A3

• (c) HLA-B27

• (d) HLA-DQ2

Q22. Subcutaneous nodules occur in up to what share of patients with rheumatoid arthritis?

• (a) 1%

• (b) never

• (c) 90%

• (d) 30%

Q23. An older woman has hard bony swellings of the distal interphalangeal joints and pain after use with brief morning stiffness. The nodes are

• (a) Heberden nodes of osteoarthritis

• (b) rheumatoid nodules

• (c) tophi

• (d) Bouchard nodes of RA

Q24. The core pathology of osteoarthritis is

• (a) progressive loss of joint cartilage with osteophytes and sclerosis

• (b) bacterial infection

• (c) autoimmune synovitis with pannus

• (d) crystal deposition

Q25. A man has an acutely painful, red, swollen first metatarsophalangeal joint. Joint fluid would show

• (a) positively birefringent rhomboid crystals

• (b) gram-positive cocci always

• (c) needle-shaped birefringent urate crystals

• (d) cholesterol crystals

Q26. Chalky deposits of urate crystals surrounded by a granulomatous reaction in gout are

• (a) tophi

• (b) rheumatoid nodules

• (c) Heberden nodes

• (d) sequestra

Q27. An elderly patient has calcification of the knee cartilage and positively birefringent crystals in joint fluid. The disorder is

• (a) rheumatoid arthritis

• (b) calcium pyrophosphate deposition (chondrocalcinosis)

• (c) septic arthritis

• (d) gout

Q28. A soft tissue sarcoma with translocation t(X;18) is

• (a) synovial sarcoma

• (b) Ewing sarcoma

• (c) rhabdomyosarcoma

• (d) myxoid liposarcoma

Q29. In adults, soft tissue sarcomas most often arise in the

• (a) heart

• (b) head and neck

• (c) extremities (45%)

• (d) trunk only

Q30. An inherited syndrome predisposing to soft tissue sarcoma is

• (a) Turner syndrome

• (b) Li-Fraumeni syndrome (TP53)

• (c) Marfan syndrome

• (d) Down syndrome

Active Recall

From memory: describe osteomyelitis routes, organisms and sites by age; place each bone tumour by age and site and give its hallmark; explain Paget disease; contrast RA, OA, gout and CPPD; and give soft tissue sarcoma sites, syndromes and translocations.