Myxoid chondrosarcoma of the synovial tissue. A clinicopathologic, histochemical, and ultrastructural analysis.

The first case of a myxoid chondrosarcoma, originating in the synovia of the joint and tendon sheaths of the ankle in a 37-year-old man, is reported. Light microscopically the tumor was similar to extraskeletal myxoid chondrosarcoma as previously described. The chondromatous nature of the tumor was further indicated by the histochemical analysis, which revealed the presence of chondroitin 4- and 6-sulphate in the tumor matrix. Ultrastructurally, chondroblast-like cells with dilated rough endoplasmic reticulum, abundant glycogen, some lipid droplets and numerous microvilli-like projections of the cytoplasm dominated. Also mitochondria-rich cells were observed as well as intermediate cell forms. Based on the observations in this case, the frequent occurrence of synovial chondromatosis, the assumed synovial origin of extraskeletal chondromas and the wide morphologic and functional spectrum synovial intima cells may cover, it is suggested that the myxoid chondrosarcoma originated from the synovial intima cells.