Osteogenic sarcoma (Osteosarcoma)

🦴⚡ Osteosarcoma is the most common primary malignant bone tumour of adolescence. It is radio-resistant ❌, so radiotherapy is usually not part of the treatment plan.

📖 About

• Most common primary malignant bone tumour in adolescents & young adults (peak age 15–18).
• Arises in the metaphysis of long bones near growth plates (rapid growth zones during puberty).
• Produces immature bone (osteoid) as its pathological hallmark.
• Most common sites: distal femur, proximal tibia, proximal humerus.

🧬 Aetiology & Genetics

• Genetic predisposition:
  • Li-Fraumeni syndrome (TP53 mutation) 🧬
  • Hereditary retinoblastoma (RB1 gene) 👁️
• Other associations:
  • Paget’s disease of bone (older adults) 🦴
  • Prior exposure to ionising radiation ☢️
• Pathology: malignant cells producing disorganised osteoid → bone destruction & replacement.

🩺 Clinical Features

• Persistent, progressive pain (often worse at night) 😣.
• Swelling & tenderness around the joint.
• Palpable, firm mass in advanced cases.
• Restricted joint movement; limp if lower limb affected.
• Pathological fracture due to weakened bone 🦴💥.
• Systemic symptoms (weight loss, fever, malaise) usually appear late.

🖼️ Classic Imaging Signs

• Plain X-ray: “Sunburst appearance” 🌞 = spiculated periosteal bone growth.
• Codman’s Triangle: periosteal elevation due to aggressive tumour growth 📐.
• MRI: Defines local extent & soft-tissue invasion (surgical planning).
• CT chest: Essential to look for lung metastases (most common site 🌬️).

🧪 Other Investigations

• Biopsy: Core/open biopsy = gold standard for histological diagnosis.
• Labs: ↑ Alkaline phosphatase & LDH → correlate with tumour burden & prognosis.
• Bone scan: Detects multifocal disease or bone metastases.

💊 Treatment

• Surgery: Mainstay of treatment 🩺✂️
  • Limb-salvage surgery now preferred in many cases.
  • Amputation still used if tumour encases vital neurovascular structures.
• Chemotherapy: 💉
  • Given pre-operatively (neoadjuvant) to shrink tumour.
  • Post-operatively (adjuvant) to eliminate micrometastases.
  • Common agents: Methotrexate, Doxorubicin, Cisplatin, Ifosfamide (MAP regimen).
• Radiotherapy: ❌ Not effective (radio-resistant).

📈 Prognosis

• With modern therapy: 5-year survival for localised disease ≈ 60–70% 🌟.
• Poorer outcomes in:
  • Axial tumours (pelvis/spine/skull).
  • Metastatic disease at diagnosis (esp. lungs) 🌬️.
  • Poor histological response to neoadjuvant chemo.

🧑‍🏫 Exam Tip

Remember the triad for imaging OSCEs: Sunburst pattern 🌞, Codman’s triangle 📐, and metaphyseal location near growth plates. Always link osteosarcoma to adolescents with bone pain + swelling and highlight that radiotherapy is not used 🚫.

📚 References

• Oxford Handbook of Oncology
• Campbell’s Operative Orthopaedics

Cases — Osteogenic Sarcoma (Osteosarcoma)

• Case 1 — Adolescent with knee pain 🦴: A 15-year-old boy presents with progressive pain and swelling around his left knee, worse at night and not relieved by rest. Exam: firm, tender mass around distal femur. X-ray: mixed lytic–sclerotic lesion with periosteal elevation (“sunburst” pattern, Codman’s triangle). Diagnosis: osteosarcoma of distal femur. Managed with neoadjuvant chemotherapy followed by limb-salvage surgery.
• Case 2 — Pathological fracture ⚡: A 17-year-old girl presents after a minor fall causing a mid-femoral fracture. History: 3 months of dull bone pain. X-ray: destructive metaphyseal lesion with cortical breach. Biopsy: malignant osteoid production. Diagnosis: osteosarcoma presenting with pathological fracture. Managed with chemo and surgical resection; orthopaedic oncology team involved.
• Case 3 — Metastatic disease 🌬️: A 14-year-old boy with known osteosarcoma of the proximal tibia (diagnosed 6 months ago) presents with cough and breathlessness. CT chest: multiple cannonball pulmonary metastases. Diagnosis: osteosarcoma with lung metastases. Managed with systemic chemotherapy, resection of primary tumour, and palliative resection of lung mets if feasible.

Teaching Point 🩺: Osteosarcoma is the most common primary malignant bone tumour in adolescents, usually affecting metaphyses of long bones (distal femur, proximal tibia, proximal humerus). Key features: progressive bone pain, swelling, pathological fractures. X-ray: sunburst periosteal reaction, Codman’s triangle. Metastasis: commonly to lungs. Management: multi-agent chemotherapy + surgical resection (limb-salvage or amputation).