MORPHOLOGICAL STUDIES OF INDUCED PULMONARY TUMORS IN MICE WITH SPECIAL REFERENCE TO THEIR CYTOGENESIS

Abstract

The strain dd adult mice received intraperitoneal injections of 10 per cent aqueous solution of urethane. Pearly-white tumors began to appear in a few weeks after the last injection. Light microscopic observations revealed that the benign adenomas arose from the alveolar region remote from any possible contact with the bronchioli. In the early stages, proliferation of the alveolar wall cells were shown by electron microscopic observations. The tumor cells are divided into three types according to their fine structures; (1) cells bearing osmiophilic bodies in their cytoplasm, which resemble the alveolar wall cells, (2) ciliated cells devoid of osmiophilic bodies, which resemble the ciliated cells of the bronchial epithelium, (3) non-ciliated cells devoid of osmiophilic bodies, which resemble in shape the cuboidal cells of the terminal bronchioli. Therefore, it is indicated that these induced pulmonary tumors in mice probably originate from the alveolar wall cells.