Abstract
Incipient growth sites of tumor cells intravenously transplanted in the lungs were investigated in animals. Three strains of ascites hepatoma (AH 66F, AH 272 and AH 601) and ACl/N rat transplantable breast cancer were used. Ascites hepatoma was transplanted into the tail vein of Donryu rat and transplantable rat breast cancer into the one of ACl/N rat. These rats were sacrificed 24-72 hours after tumor inoculation. The identification of different types of pulmonary blood vessels was made by micropaque (aquous barium sulfate) injection. The following results were obtained by histological examination of removed lungs.
The tissue spaces adjacent to pulmonary venules afforded the initial growth of AH66F. Both the inside and outside, or the inside of pulmonary arterioles afforded the one of transplantable rat breast cancer. Tumor embolus within capillaries or proliferation of tumor cells in the outside of capillaries was observed in the lungs of animals transplanted with AH272 or AH6O1.
The above results will mean that initial pulmonary metastasis might be formed not only by the growth of tumor cells embolized in arterioles or capillaries but also by the growth of tumor cells extravasated from venules.
