Gonadoblastoma: immunohistochemical localization of Müllerian-inhibiting substance, inhibin, WT-1, and p53.

Gonadoblastomas are rare tumors composed of both germ cells and sex-cord cells. In this study, we investigated two such tumors for the expression of the Wilms' tumor gene (WT1), which has a key role in urogenital development, and the expression of markers associated with sex-cord differentiation, i.e., Müllerian-inhibiting substance (MIS) and inhibin (I). We also studied p53 expression. Archival, paraffin-embedded tissue from two patients with gonadoblastoma, one bilateral and both with concurrent germinomatous areas, were evaluated immunohistochemically with antibodies directed against I, MIS, WT1, and p53. I was noted in the sex-cord component of the gonadoblastoma and not in germinoma cells. MIS was noted in both, although it was more strongly expressed in the sex-cord component. p53 expression was noted in the germ cells of the gonadoblastoma, as well as in the frankly germinomatous areas, whereas WT1 was found only in the sex-cord region and not at all in the germ cells of either of our two cases. These findings lead us to propose that WT1 and I are present in the initiation of gonadoblastomas, but are lost with the progression of these tumors. Similarly, MIS may be involved in its tumorigenesis. The expression of p53 seems to support the concept that gonadoblastoma represents in situ germ cell neoplasia with malignant potential. Additional studies, however, are needed to validate this concept.