Immunohistochemical analysis for desmin in normal and neoplastic ovarian stromal tissue

Ovarian stroma contains cells with the ultrastructural features of smooth-muscle cells. The purpose of this study was to analyze normal ovaries, ovarian stromal tumors (fibroma/thecomata and granulosa cell tumors), and ovarian leiomyomata for desmin reactivity. Groups of ovarian stromal cells that expressed desmin were noted in six of six normal ovaries. Desmin was also detected in two of six fibroma/thecomata and two of two ovarian leiomyomata. The number of tumor cells with detectable desmin was much greater in the leiomyomata. Desmin was not detected in any of six granulosa cell tumors. We conclude that stromal cells with an immunohistochemical feature of smooth-muscle cells are routinely found in normal ovaries. This study demonstrates the usefulness of immunohistochemistry in corroborating the diagnosis of ovarian leiomyomata, although desmin positivity per se is not diagnostic of ovarian leiomyomata, and also raises the possibility that some ovarian leiomyomata may be derived from stromal cells.