We report the case of a 60-year-old woman with endometrial mucinous adenocarcinoma. Endometrial cytology showed tumor cells arranged in papillary and complex ductular structures. Although the diagnosis of endometrial adenocarcinoma was initially considered based on the cytological findings, the low nuclear : cytoplasmic ratio and polarity of the tumor cells prevented a definitive cytological diagnosis. Pathological examination of the resected specimen revealed that most of the tumor cells were cuboidal and contained intracellular mucin, the cells resembling those of the endocervical type of mucinous adenocarcinoma. Thus, we finally made the pathological diagnosis of endometrial mucinous adenocarcinoma.
