Association of endometrial epithelial metaplasias with endometrial carcinoma and hyperplasia in Japanese and American women.

We reviewed endometrial tissue from 166 cases of endometrial adenocarcinoma and hyperplasia--91 seen at Kyushu University, Fukuoka, Japan, and 75 at George Washington University, Washington, D.C., U.S.A.--to compare the prevalence of epithelial metaplastic changes in the two populations. Metaplasias were more common in the benign endometrium associated with carcinoma at George Washington University (78%) than at Kyushu University (54%). They were associated with carcinomas of lower grade and accompanied by hyperplasia at both institutions. These results indicate that endometrial metaplasias, like endometrial hyperplasias, tend to be associated with less virulent endometrial carcinomas and to be more common in American women (who represent a high-risk population for endometrial carcinoma) than in Japanese women (in whom the risk is low but rising.