A 32-year-old woman notices a slowly growing, painless lump behind the right knee. X-ray shows a densely ossified mass attached to the posterior surface of the distal femoral metaphysis, sitting on the cortex without involving the medullary canal. CT confirms no medullary continuity. Biopsy shows a well-differentiated fibro-osseous tumour with parallel trabeculae of mature bone. The most appropriate treatment is:

• A Neoadjuvant chemotherapy followed by wide resection
• B Wide local resection without chemotherapy ✓
• C Intralesional curettage and bone grafting
• D Radiotherapy followed by limb salvage surgery

Explanation

Parosteal (juxtacortical) osteosarcoma arises on the bone surface, classically the posterior distal femur of young adults, shows no medullary involvement, and is a low-grade tumour with the best prognosis of all osteosarcoma variants. Treatment is wide surgical resection alone, since it has low metastatic potential and chemotherapy adds nothing. Intralesional curettage causes recurrence, and radiotherapy has no role. Medullary invasion signals higher-grade dedifferentiation.

Reference: Bailey and Love's Short Practice of Surgery, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.