Cell degeneration and necrosis in experimental gliomas.

Cell degeneration and necrosis in ethylnitrosourea-induced gliomas of rats were examined using light and electron microscopy. Two types of cell loss were observed: massive necrosis and individual cell death. Massive necrosis was influenced by the size, malignancy and histological type of the gliomas: it occurred most frequently in large, malignant pleomorphic gliomas and epindymomas. Proliferation of endothelial cells, narrowing of vascular lumina and degenerative changes affecting vessel walls were thought to be the major factors causing necrosis. Individual cell death occurred throughout the neoplasms irrespective of their size. Progressive degenerative changes, involving both the nucleus and cytoplasm, preceded cell death. Macrophages (both microglial and monocytic in origin). reacting astrocytes and, to a lesser extent, neoplastic glial cells engulfed and digested the necrotic cells and their remnants.