We report a case of
adenomyoma of endocervical type arising in a 44-year-old female. Grossly, a well-circumscribed
tumor protruding from the right side of the uterine cervix was seen which was assumed to be an ovarian
tumor by imaging studies carried out preoperatively. The
tumor was composed of a mixture of proliferating glands of endocervical type and fascicles of smooth muscle cells. There was no distinct nuclear
anaplasia in the proliferating glands, there were no architectural abnormalities, and there was no evidence of destructive stromal invasion such as desmoplasia. Minimal deviation
adenocarcinoma, which shows a gastric phenotype with immunoreactivity for M-GGMC-1 and predominantly PAS-positive neutral
mucin, was a serious diagnostic possibility, but the lesion was well-circumscribed, cytologic and architectural abnormalities were absent, and staining for M-GGMC-1 was negative, which suggested a diagnosis of endocervical
adenomyoma. An increased Ki-67 labeling index by up to 20%, the presence of predominantly PAS-positive neutral
mucin, and membranous immunoreactivity for CEA in limited areas were diagnostic pitfalls, which could lead to an erroneous diagnosis of minimal deviation
adenocarcinoma of the uterine cervix. Therefore, the results of these ancillary techniques should be interpreted with caution and combined with gross and light microscopic features.