Orthopedic Oncology and Musculoskeletal Tumors
Principles of Orthopedic Oncology
Candidates must understand benign vs malignant tumors, staging (Enneking, TNM), imaging (X-ray, MRI, CT, bone scan), biopsy principles (core biopsy preferred, avoid contamination), and treatment (limb salvage, amputation, chemotherapy, radiation). Know common tumors by age and location.
Key Concepts
- Benign bone tumors: Osteochondroma (exostosis, cartilage cap), enchondroma (lytic lesion, calcifications), non-ossifying fibroma (NOF, eccentric, sclerotic rim), giant cell tumor (epiphyseal, soap-bubble appearance, around knee), unicameral bone cyst (proximal humerus, fallen fragment sign).
- Malignant bone tumors: Osteosarcoma (most common primary bone cancer, metaphysis of long bones, sunburst appearance, Codman triangle), Ewing sarcoma (diaphysis, onion-skin periosteal reaction, small round blue cells), chondrosarcoma (adult, pelvis, cartilage matrix).
- Soft tissue sarcomas: Liposarcoma, synovial sarcoma, rhabdomyosarcoma (children).
- Metastatic bone disease: Most common bone tumor overall; breast, prostate, lung, kidney, thyroid. Pathologic fracture risk (Mirels score).
- Staging: Enneking (benign: latent, active, aggressive; malignant: stage I (low grade), II (high grade), III (metastasis)).
Traps
- Biopsy: Must be performed by the surgeon who will do the definitive resection, in a way that does not contaminate other compartments.
- Osteosarcoma: Often presents with pain and swelling in adolescent; X-ray shows aggressive features. Neoadjuvant chemotherapy improves survival.
- Giant cell tumor: Can be aggressive; treatment is curettage and cementing or resection.
- Mirels score: >8 indicates prophylactic fixation for impending pathologic fracture.
Worked Example
A 15-year-old boy presents with knee pain and swelling. X-ray shows a destructive lesion in the distal femur with sunburst appearance and Codman triangle. Diagnosis: osteosarcoma. Rule of thumb: Osteosarcoma is the most common primary bone malignancy in adolescents; treat with neoadjuvant chemotherapy, wide resection, and reconstruction. Biopsy should be done by the treating surgeon.