From the archives of the AFIP. Extraskeletal osseous and cartilaginous tumors of the extremities.

Abstract

Extraskeletal osseous and cartilaginous tumors and tumorlike conditions of the extremities can often be differentiated radiologically; for those that cannot, knowledge of the spectrum of lesions will allow a suitably ordered differential diagnosis. Of the osseous lesions--myositis ossificans, fibro-osseous pseudotumor, fibrodysplasia ossificans progressiva, soft-tissue osteoma, and extraskeletal osteosarcoma--all but myositis ossificans are relatively rare. Myositis ossificans has a distinct mineralization pattern that can be observed radiologically as a peripheral rim of lamellar bone. Fibro-osseous pseudotumor typically occurs in the digits of the hand and lacks the well-defined zoning pattern of myositis ossificans. The cartilaginous entities include the true tumors, soft-tissue chondroma and extraskeletal chondrosarcoma, and the tumorlike process, synovial osteochondromatosis. The tumors are relatively rare; synovial osteochondromatosis commonly affects middle-aged men, especially in the knee, and is associated with osteoarthritis. The differential diagnosis for these extraskeletal osseous and cartilaginous lesions includes soft-tissue sarcoma, benign mesenchymoma, malignant mesenchymoma (rare), calcified tophi in gout, melorheostosis (rare), pilomatricoma (rare), and tumoral calcinosis (rare).