"Surface epithelial changes" in uterine endometrioid carcinoma mimicking micropapillary serous borderline tumor of ovary: report of two cases and review of the literature.

We encountered two cases of endometrioid carcinoma of uterus with extensive surface epithelial changes (SECs) mimicking serous borderline tumor (SBT) of the ovary. The first case was a well-differentiated endometrioid carcinoma arising in a background of complex atypical hyperplasia. The second case was moderately-differentiated endometrioid carcinoma with squamous and mucinous differentiation. The SECs comprised of thin microapapillae without hierarchal branching, lined by cuboidal cells with eosinophilic cytoplasm and mild to moderate nuclear atypia. These areas were reminiscent of SBTs of ovary, micropapillary type. This report expands the existing spectrum of SECs. Serous borderline tumor of ovary like surface epithelial changes could be misleading if present in an endometrial biopsy or curettings. Therefore, knowledge of this morphologic variation is important.