Chondrosarcoma is a primary malignant bone tumor typically found in older adults (> 60 yr). The shoulder and pelvic girdles, knee, and spine are common locations for these chondrogenic lesions.1 The lesions have a typical "ring and arc" pattern or "popcorn" calcifications on plain radiographs. Histologic evaluation typically reveals multiple cells per lacunae, mitotic activity, and pleomorphism. Immunohistochemical staining is often S-100 positive. Wide resection is typically the treatment of choice for these tumors.1 This patient is too old to have a chondroblastoma, and the radiographic (typically distinct sclerotic border) and histologic (chondroblasts) findings are inconsistent for this lesion. Similarly, the radiographic findings are not consistent with a bone-forming tumor as seen with an osteosarcoma. Multiple myeloma is a small round blue cell tumor without specific lacunae. Desmoplastic fibroma, a rare tumor that is locally destructive and benign, would not demonstrate an aggressive, malignant process as seen in Figure 3.
1. Gibbs CP Jr, Weber K, Scarborough MT. Malignant bone tumors. Instr Course Lect 2002;51:413-28.
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