Poorly differentiated ovarian Sertoli-Leydig cell tumor with smooth muscle differentiation masquerading as leiomyosarcoma: a case report

Ovarian Sertoli-Leydig cell tumors (SLCTs) are rare sex cord-stromal neoplasms. Poorly differentiated SLCTs can harbor heterologous elements, among which myogenic differentiation poses a significant diagnostic challenge [1–3]. A 45-year-old female patient presented with abdominal pain and large pelvic masses. Initial core needle biopsy suggested leiomyosarcoma, showing a malignant spindle cell proliferation positive for smooth muscle actin (SMA), desmin, and mutant-type p53. However, upon examination of the fully resected specimen, a biphasic tumor comprising intermingled epithelioid and spindle cells was identified. An expanded immunohistochemical analysis subsequently revised the diagnosis to a poorly differentiated Sertoli-Leydig cell tumor (SLCT) with smooth muscle differentiation. The patient underwent five cycles of chemotherapy with paclitaxel and carboplatin and remained free of recurrence at the 6-month follow-up. The tumor closely mimicked a primary leiomyosarcoma. Diagnostic precision was achieved through identification of biphasic architecture in the surgical specimen and demonstration of diffuse, robust nuclear positivity for the sex cord-stromal marker SF-1, which superseded the misleading focal expression of myogenic markers. This case highlights the critical importance of including Sertoli-Leydig cell tumor (SLCT) in the differential diagnosis of pelvic spindle cell tumors. Utilizing a comprehensive immunohistochemical panel that incorporates sex cord-stromal markers is imperative to avoid diagnostic inaccuracies and to facilitate appropriate clinical management.