Malignant Bone Tumours: NEET PG High-Yield
Orthopedic Oncology: Aggressive Lesions
1. Key Malignant Bone Lesions
| Tumour | Key Features (High-Yield) |
|---|---|
| Osteosarcoma | The most common primary malignant bone tumour in young adults. Codman triangle, Sunburst appearance. Metaphyseal. |
| Ewing Sarcoma | “Onion-skin” periosteal reaction. Diaphyseal. t(11;22) translocation. Small, round blue cells. |
| Chondrosarcoma | Tumour of older adults. “Popcorn calcification” on X-ray. Resistant to chemo/radiotherapy (Surgery is the mainstay). |
| Multiple Myeloma | Most common primary bone malignancy (overall). “Punch-out” lytic lesions. M-spike on SPEP. |
2. NEET High-Yield Pearls
- Location is Key: Osteosarcoma is metaphyseal (around the knee). Ewing Sarcoma is diaphyseal. GCT is epiphyseal.
- Codman Triangle: Represents periosteal elevation by a rapidly growing tumour; classic for Osteosarcoma.
- Ewing Sarcoma Histology: CD99 positive. The t(11;22) translocation involves the EWS-FLI1 fusion gene.
- Metastasis: Always remember that metastatic disease is far more common in bone than primary bone malignancy. Primary sites to rule out: Breast, Lung, Thyroid, Kidney, Prostate (mnemonic: BLT with a Kosher Pickle).
- Alkaline Phosphatase (ALP): Often elevated in Osteosarcoma (and Paget’s disease), serving as a marker for bone turnover.