[Neoplastic chondroneogenesis as a characteristic of mesenchymal chondrosarcomas]

Mesenchymal chondrosarcomas are rare skeletal malignancies, which are typically characterized by tumor compartmentation. One tumor area is formed by small, undifferentiated neoplastic cells, whereas the second compartment is composed of cartilaginous areas. In this study, the application of in situ detection techniques enabled us to characterize the different tumor compartments according to their cellular differentiation patterns. The use of characteristic marker genes identified all steps of chondrogenesis within the different tumor compartments. Undifferentiated tumor cells in the small-cell areas were negative for vimentin and the cytoprotein S-100, whereas other tumor cells expressed collagen type IIA and vimentin indicating a chondroprogenitor cellular phenotype in these small-cell areas. Fully differentiated chondrocytic cells expressing collagen type II were found in the chondroid areas. The focal expression of type X collagen indicated hypertrophic differentiation of the neoplastic chondrocytes. The results characterize mesenchymal chondrosarcomas as skeletal malignancies that arise from undifferentiated chondroprogenitor cells and have the potential to undergo all steps of chondrocytic differentiation.