Electron microscopic studies of placental and uterine tumors induced in rats

The ultrastructure of eight 7,12-dimethylbenz (a) anthracene (DMBA) or 4-nitroquinoline-N-oxide (4-NQO) induced malignant tumors of placental and uterine origin in the rat were studied. Three of eight tumors had the ultrastructural characteristics of choriocarcinoma. The other five tumors had different fine structures. Two were classified as squamous cell carcinoma, one was as a leiomyosarcoma and the other two were undifferentiated sarcoma.