Adenomatoid tumors of the female and male genital tracts express WT1

Adenomatoid tumors are benign proliferations most often encountered in the female and male genital tracts. The mesothelial phenotype of these unusual tumors has been established by a variety of ultrastructural and immunohistochemical studies, although their etiology is by no means certain. The expression of the Wilms' tumor suppressor gene, WT1, in normal, hyperplastic, and malignant mesothelial cells prompted us to analyze the expression pattern of WT1 in a series of 24 adenomatoid tumors occurring in the uterus, fallopian tube, ovary, epididymis, scrotum, and testis. Twenty-three of the tumors expressed WT1 protein and the same number expressed calretinin, another marker of mesothelial differentiation. The one tumor that failed to stain with calretinin was positive for WT1. These results provide further support for mesothelial differentiation of adenomatoid tumors and suggest that the presence of WT1 expression may be useful in the differential diagnosis of these uncommon neoplasms, especially when they present in unusual settings or expression of other mesothelial markers is absent.