Osteosarcoma of the maxilla. Case report and ultrastructural study.

An osteosarcoma, occurring in the maxillary alveolar ridge of a 17-year-old girl is presented. The tumor consisted predominantly of pleomorphic, mainly osteoblast-like and anaplastic cells. At the ultrastructural level the osteoblast-like cells were characterised by excentrically situated lobed nuclei, extensively swollen, dilated and rough endoplasmic reticulum (RER), polymorphism of mitochondria and sparse Golgi-systems. The undifferentiated cells were characterized by large, electron-lucent nuclei and paucity of non-dilated RER and mitochondria. The intercellular matrix contained collagen fibers with areas of focal collections of calcification.