Uterine tumor resembling ovarian sex cord tumor (UTROSCT). Report of case suggesting neoplastic origin of intratumoral myoid cells.

We report a case of double uterine tumor resembling ovarian sex cord tumor (UTROSCT). The tumor was composed of sex cord-like cords, nests and tubules, and bundles of myoid cells. The lesion was interesting especially in regard to histogenesis of intratumoral myoid cells. It is not known whether these cells are neoplastic or whether they represent preexisting myometrial smooth muscle cells entrapped into the tumor. In the present case, the sex cord-like epithelioid cells showed immunohistochemically myoid features in addition to features of epithelial, sex cord and endometrial stromal differentiation. The spindle cells expressed myoid, epithelial and endometrial stromal markers, but some of them were positive for sex cord marker calretinin. This immunophenotypic overlap between sex cord-like and myoid spindle elements indicates that the spindle cells of UTROSCT represent divergent line of differentiation of neoplastic cell rather than entrapped myometrial cells. It further expands the spectrum of possible differentiations in this polyphenotypic neoplasm.