[Histogenesis of the skeleton and morphogenesis of cartilage-forming neoplasias].

Aims: Fetal skeletogenesis has been extensively investigated in the vertebrates and both, cellular phenotypes and regulatory mechanisms are well characterized. This knowledge has been used in the past years to elucidate the biology of mesenchymal neoplasias of the skeleton, in particular of the cartilage forming tumors.

Results: The hallmark of chondrogenic tumors is the presence of cells, which can show the full differentiation potential of physiologic chondrocytes depending on the tumor entity investigated. The phenotypic plasticity of chondrocytes explains the striking heterogeneity of cells and extracellular matrix found not only in between different, but also within chondrogenic tumor types. Hereditary exostosis is one example for which genetic analysis as well as the knowledge of regulatory pathways have contributed to our understanding of tumor development: the deficiency in functional EXT gene products explains the pathogenesis of these neoplasms.

Conclusions: In principle, chondrogenic neoplasias follow differentiation rules delineated during fetal skeletogenesis. Tumor classifications, so far based only on histomorphological criteria can be extended by molecular markers, which have the potential to contribute to a biology-orientated classification of skeletal neoplasms