Ultrastructural cytology of human osteosarcoma cells.

The cytology of 6 osteosarcomas was examined by electron microscopy. In keeping with the varied pattern of osteosarcomas seen by light microscopy several types of tumor cells could be differentiated: osteoblast-like, fibroblast-like, chondroblast-like, osteoclast-like and histiocyte-like cells. Moreover, atypical malignant mesenchymal cells and vascular spaces were present. The individual cytoplasmic organelles are not considered to be specific to particular types of cell as seen from the discussion of the significance of rough endoplasmic reticulum, microfilaments and lysosomes. Only examination of the composite pattern of subcellular organelles allows the differentiation of certain cell types. All tumor cells visible in osteosarcomas are considered as modifications of a transformed common progenitor cell. Because of the variegated cytological picture a multipotent mesenchymal cell rather than an osteoblastic cell is assumed to be the ancestor cell.