Microcarcinoma of the endometrium: a mapping study with special reference to cytologic atypia in the endometrium.

In order to elucidate the basis for the development of an endometrial carcinoma, we looked for microcarcinomas measuring < 5 mm in greatest diameter, and studied their histologic characteristics and those of the neighboring endometrium. Using serial step section methods, two microcarcinomas were detected. A microcarcinoma was found in one of 14 uteri resected for atypical hyperplasia and the other was found in one of 114 uteri resected for endometrial carcinoma. The neighboring endometrium of the former was adenomatous and had atypical hyperplasia and that of the latter was atrophic and contained atypical glands characterized by cytologic atypia and not by architectural changes. The findings may suggest endometrial carcinomas to have two pathogenetic forms: a carcinoma associated with hyperplasia and occurring in premenopausal women, a second carcinoma associated with atrophic endometrium and occurring in postmenopausal women. Atypical glands in atrophic endometria may indicate that endometrial specimens from postmenopausal women should be carefully screened for cytologic atypia.