[Matrix gene expression pattern as indicators of the biology of cartilage-forming tumors]

Mesenchymal cells can be characterized by the expression of specific sets of extracellular matrix (ECM) proteins. The aim of our study was to identify such expression pattern in cartilage-forming tumours in order to elucidate the biology of these neoplasms. In situ hybridisation and immunohistochemistry for various ECM components were performed on enchondromas, conventional chondrosarcomas of various grades and dedifferentiated chondrosarcomas. Chondroid areas of all investigated neoplasms showed strong expression of cartilage collagen types II and IX and aggrecan core and link protein. Focally, also the expression of other collagen subtypes such as collagen type X and collagen types I and III was observed. Non-chondroid areas of dedifferentiated chondrosarcomas lacked any expression of the cartilage-typical gene products and were instead positive for interstitial collagen types I, III, and VI. The hallmark of all investigated cartilaginous neoplasms was the expression of the chondrocyte-typical genes. Neoplastic chondrocytes showed the differentiation facettes similar to their physiological counterparts resulting in the high heterogeneity, which is characteristic for chondrogenic neoplasms. A different biology is suggested for dedifferentiated chondrosarcomas, in which the "dedifferentiated" portion is proposed to have a separate (e.g. fibroblastic) mesenchymal origin.