Ovarian involvement by desmoplastic small round cell tumor with leydig cell hyperplasia showing an unusual immunophenotype (cytokeratin negative, calretinin and inhibin positive) mimicking poorly differentiated sertoli leydig cell tumor.

Desmoplastic small round cell tumor (DSRCT) is a rare aggressive tumor primarily involving serosal surfaces in adolescents and young men. Diagnosis is based on specific clinicomorphologic, immunohistochemical, and genetic features. We report here a variant of DSRCT involving the ovaries that mimics the Sertoli-Leydig cell tumor in a 21-year-old woman complaining of abdominal pain. Abdominal ultrasonography and computed tomography showed a right adnexal mass. She had a slightly raised serum CA-125 level. Frozen section examination identified the right ovarian mass as a poorly differentiated Sertoli-Leydig cell tumor. The surgically resected tumor and left ovary and omentum implants found during laparoscopy were diagnosed as DSRCT with Leydig cell hyperplasia. Immunohistochemically, the tumor cells were negative for epithelial markers but were positive for calretinin and inhibin. The patient is still undergoing chemotherapy at 8 months after initial presentation with partial response. This case showed that DSRCT with unusual immunohistochemical profiles and Leydig cells hyperplasia pose a diagnostic challenge. Molecular genetic techniques may help in these cases.