Pleomorphic ("dedifferentiated") chondrosarcoma. Report of a case initially examined by fine needle aspiration biopsy.

Fine needle aspiration (FNA) biopsy of a predominantly radiolucent, destructive lesion of the right distal femoral metaphysis of a 69-year-old man produced smears containing spindle-shaped cells with cytologic features consistent with a malignant fibrous histiocytoma. This initial diagnosis was supported by immunoperoxidase staining, which was strongly positive for vimentin and alpha-1-antichymotrypsin, focally positive for S-100 protein and negative for desmin, muscle-specific actin, keratin, carcinoembryonic antigen and epithelial membrane antigen. Subsequent surgical resection revealed a lesion with a predominance of malignant fibrous histiocytoma-type regions; however, focal microscopic areas contained a low-to-medium-grade cartilaginous component. The final diagnosis rendered was thus pleomorphic or so-called "dedifferentiated" chondrosarcoma. This rare lesion should be included in the differential diagnosis of malignant spindle-cell lesions of bone assessed by FNA biopsy.