Musculoskeletal Oncology
Core concepts
Oncology questions emphasize systematic evaluation and staging. Know the Enneking staging system (benign latent/active/aggressive; malignant stages I-III) and the role of the biopsy (the wrong biopsy can cost a limb). Understand the difference between benign and malignant bone lesions by age, location, and margin (e.g., osteochondroma, enchondroma, giant cell tumor, osteosarcoma, Ewing sarcoma, chondrosarcoma). Master the principles of limb-salvage surgery and the indications for amputation. Know soft tissue sarcoma: size, depth, grade, and the importance of wide margins and radiation. Review metastatic bone disease: the workup of a pathologic fracture, the role of bisphosphonates/denosumab, and the Mirels score for prophylactic fixation. Recognize the red flags: night pain, unintentional weight loss, and a mass that is deep or enlarging.
Traps
The classic trap is biopsying a presumed benign lesion without imaging or a multidisciplinary plan. Another is missing a pathologic fracture as the first sign of malignancy. Examiners also test the difference between osteosarcoma (young, metaphyseal, sunburst) and Ewing sarcoma (diaphyseal, onion-skin, systemic symptoms).
Rule of thumb
Any bone lesion with aggressive features (wide zone of transition, cortical destruction, periosteal reaction) should be referred to a sarcoma center before biopsy.
Worked example
A 16-year-old with knee pain and a distal femoral metaphyseal lesion with a sunburst pattern: suspect osteosarcoma; obtain staging imaging and refer for neoadjuvant chemotherapy and limb-salvage resection.