ULTRASTRUCTURAL APPEARANCE OF CHONDROBLASTOMA

The ultrastructural appearance of two chondroblastoma were examined by scanning and transmission electron microscopy. The polygonal basal ce lls, with a scanty pericellular matrix, show a poorly developed endopl asmic reticulum and many Golgi bodies. The highly differentiated chond roid cells are assembled in isogenous clusters and show intracytoplasm ic inclusions of glycogen and lipids, numerous mitochondria and su per ficial secretion vesicles arising from a well developed rough endoplas mic reticulum. Clusters of crystals, in close contact with the matrix collagen fibres, are found near to the tumour cells. These ultrastruct ural characteristics, together with the basal undifferentiated cells t hat proliferate and differentiate into cartilaginous tissue, distingui sh this neoplasm from chondroma, mesenchymal chondrosarcoma and chondr omyxoid fibroma and confirm its chondroid origin.