Ultrastructure of mammary carcinomas in male rats induced by 7,12-dimethylbenz(a)anthracene.

The morphology of mammary tumors induced by 7,12-dimethylbenz(a)anthracene in male rats was investigated by light and electron microscopy. All tumors induced in male rats were carcinomas with prominent epithelial growth which shows a medullary or cribriform appearance. Neither mammary dysplasias nor fibroadenomas were induced in male rats. Foci of adenoid cystic carcinoma were encountered in some parts of tumors. Papillary and/or tubular patterns, which have been observed frequently in mammary carcinomas in female rats, were not prominent histologic features in male rats. Secretory activity was not remarkable. The morphology of mammary carcinomas in male rats was unchanged in primary and transplanted tumors under various hormonal conditions. This finding supports our previously published results that the mammary carcinomas in male rats are hormone-independent, although our previous biochemical study revealed that the tumors contain both estrogen and estrogen-dependent progesterone receptors.