Immunohistochemical analysis of uroplakins, urothelial specific proteins, in ovarian Brenner tumors, normal tissues, and benign and neoplastic lesions of the female genital tract

Uroplakins are the characteristic integral membrane proteins in terminally differentiated, superficial urothelial asymmetric unit membrane. Brenner tu mors of the ovary and Walthard cell nests of Fallopian tubes have been cons idered to represent urothelial differentiation in the female genital tract, but no definitive differentiation marker has been demonstrated supporting such a conclusion. An immunohistochemical analysis was performed to assess the expression of uroplakins in these lesions as well as in various benign and neoplastic lesions and normal tissues of the female genital tract. Foca l expression of uroplakins was observed on the luminal surface of ovarian B renner tumor cells forming microcysts in all 5 cases examined. In contrast, uroplakins were slightly expressed in only 1 of 12 cases of Walthard cell nests, even in the presence of microcyst formation. Uroplakins were not exp ressed in other benign or malignant lesions or normal tissues of the female genital tract. These results support the hypothesis that the Brenner tumor and possibly Walthard cell nests represent urothelial (transitional cell) differentiation.