A 27-year-old woman was admitted to a hospital with a mass in the abdomen in which ovarian carcinoma was suspected clinically and radiologically. Computed tomography showed localized thickenings which were thought to represent tumor implants on the anterior abdominal wall. Ultrasonography revealed a solid mass of 13 cm in its maximum diameter in the right adnex which extended to the midline of the pelvic region. Doppler examination showed a conspicious vascularization in the centre of the tumor, the pattern of which was consistent with an ovarian tumor. Bilateral salpingo-oophorectomy, omentectomy, splenectomy, and appendectomy were performed due to the presence of widespread ascitis and anuric clinical picture of the patient and unresponsiveness to the treatment. Macroscopically, it was observed that bilateral ovari-es, omentum, spleen, and appendix vermiformis were infiltrated by the tumor in a widespread manner. Microscopically, a tumor consisting of small monotonous cells having round to ovoid, hyperchromatic nuclei with scant eosinophilic cytoplasm in a desmoplastic stroma was observed in the aforementioned areas. Immunohistochemically, the tumor cells showed reactivity for des-min, vimentin, synaptophysin, high molecular weight-cytokeratin, epithelial membrane antigen, and CD56. On the basis of clinical, radiological, macroscopical, microscopical, and characteristic immunohistochemical findings, the case was diagnosed as desmoplastic small round cell tumor (DSRCT). The patient received chemotherapy but died soon after the operation. DSRCT can show ovarian involvement and can mimic primary ovarian tumors so this entity should be kept in mind in young patients who have adnexial mass.

Keywords: desmoplastic small round cell tumor, ovarian tumor, small round blue cell tumor, differential diagnosis