ELECTRON MICROSCOPIC STUDIES OF PLACENTAL AND UTERINE TUMORS INDUCED IN RATS

was the fist to report benzpyrene induced chorion-epitheliomatous tumor in the rat in 1960. In 1966 SHINTANI~ reported on the experimental induction of malignant tumors of placental and uterine origin in the rat by means of local application of DMBA. MIYMAOTOV in 1971 succeeded in experimentally inducing choriocarcinoma in rats following Shintani’s modified method and in 1974 pointed out the presence of a 3-beta-01 dehydrogenase enzyme system, which is required for the synthesis of progesterone from pregnenolone. SOB IS^ (1973) introduced the in-utero tumor induction by murine sarcoma virus. Among these studies only SOBIS’S report has included ultrastructural descriptions. SOBIS classified their tumors into three different histologic types, namely yolk-sac tumor, teratoma with embryonal carcinoma and carcinosarcoma. SEKINTANI~ et al. classified their tumors as choriocarcinoma, sarcoma and carcinosarcoma of the uterine wall, adenocarcinoma of the endometrium, malignant mesothelioma, adenoacanthoma, and squamous cell carcinoma. We classified our eight tumors into choriocarcinoma, squamous cell carcinoma, leiomyosarcoma and undifferentiated sarcoma. The present report is the first one describing the ultrastructural features of malignant tumors of placental and uterine origin in the rat induced by chemical carcinogen.