Clear cell chondrosarcoma is a rare mesenchymal
neoplasm of unclear differentiation. Besides having a chondrogenic nature, an osteogenic differentiation was also proposed. In this study, expression analysis of extracellular matrix genes, which are specific for different mesenchymal cell differentiation pathways, were used to get a better understanding of origin and differentiation pattern of the
clear cell chondrosarcoma tumor cells. Our in situ analysis of two cases shows that (1) chondrocytic cell differentiation as marked by the expression of
cartilage collagen type II and
proteoglycans is a characteristic feature within the development of the
neoplasm, (2) multifocal chondrocyte
hypertrophy as shown by the expression of
type X collagen does occur, and (3) no significant expression of
collagen type I, the main gene product of osteoblastic cells, is found by the neoplastic cells. Thus, our study indicates that
clear cell chondrosarcoma shows a chondrogenic, but not osteogenic, differentiation and represents a true
chondrosarcoma. The unusual scarcity of its extracellular and the multifocal expression of
type X collagen marks
clear cell chondrosarcoma as a
chondrosarcoma tumor entity of a particular cell differentiation pattern. The expression of cartilage type
collagens represents a distinct marker from bone
metastases of clear cell
neoplasms of other origins.