A STUDY ON THE INVASIVE GROWTH OF MALIGNANT TUMORS II. ULTRASTRUCTURAL FEATURES OF THE METASTATIC GROWTH OF YOSHIDA ASCITES HEPATOMA 7974 IN THE RAT BRAIN

摘要

Donryu rats were injected into the right common carotid artery with Yoshida ascites hepatoma AH 7974 cells and two hundred serial ultra‐thin sections of six small perivascular metastatic nodules of the cerebral cortex were examined under the electron microscope. The nodules were 30 to 68 μ in diameter and consisted of 6 to 12 tumor cells. The capillaries in these metastases were closely surrounded by the tumor cells and perivascular astrocytes were lost. Most of the tumor cells were light and swollen, with only a few dark tumor cells. Pinocytic vesicles were prominent in the tumor cell cytoplasmic projections which were in direct contact with capillary basement membranes and macrophages. Lysosomes could hardly be seen in the tumor cells. At the periphery of the metastatic nodules, several macrophages with prominent phago‐lysosomes were identified. Endothelial mitosis was found in only a larger metastasis.The findings indicate that most hepatoma cells in the early perivascular metastatic nodules are degenerative, and that the lysosomal enzymes and phagocytosis of tumor cells play only a small role in the destruction of the host tissues. The main response of the host in early metastasis is the appearance of macrophages at the periphery. Endothelial mitosis does not occur until metastases grow to a certain