Abstract
Histopathological studies on the incipient metastasis formation were made on the specimens of 23 cases with surgical resection for secondary lung cancer.
There were found 15 cases with microscopic metastases following the histological examination on the area without any visible macrometastases of resected specimens.The growth of tumor cells was observed in eight cases in the tissue spaces adjacent to small blood vessels, in three within small blood vessels and those surrounding tissues, and in one within terminal bronchiole.In the remaining three cases the growth sites of tumor cells were undetermined.
From our results of animal experiments on the initial formation of pulmonary metastases via haematogeneous route, the small blood vessels were considered to be venules when cancer cells proliferated in those surrounding tissues, and to be arterioles when cancer cells proliferated both within and surrounding tissues of those vessels.
The above results will mean that initial pulmonaly metastasis via haematogeneous route in humanbeings as well as in animals, might be formed not only by the growth of tumor cells embolised in arterioles or capillaries but also by the growth of tumor cells extravasated from venules.
