Rare Ovarian Sertoli-Leydig Cell Tumor Mistaken for Leiomyosarcoma in 45-Year-Old Woman

A rare ovarian tumor that closely imitated a muscle-derived cancer has been described in a newly published case report, highlighting how easily such lesions can be misdiagnosed and how expanded immunohistochemical testing can set the record straight.

The report, published in Discover Oncology on 27 October 2026, documents the case of a 45-year-old woman who presented with abdominal pain and large pelvic masses. An initial core needle biopsy suggested leiomyosarcoma, a malignant tumor of smooth muscle, showing a malignant spindle cell proliferation that tested positive for the smooth muscle markers SMA and desmin, as well as mutant-type p53.

The diagnostic picture changed only when pathologists examined the fully resected specimen. Instead of a single spindle cell population, they identified a biphasic tumor composed of intermingled epithelioid and spindle cells, a pattern inconsistent with the initial biopsy interpretation.

An expanded immunohistochemical analysis then revised the diagnosis to a poorly differentiated Sertoli-Leydig cell tumor with smooth muscle differentiation. Sertoli-Leydig cell tumors are rare sex cord-stromal neoplasms of the ovary, and poorly differentiated forms can harbor heterologous elements, among which myogenic differentiation poses a significant diagnostic challenge.

The decisive finding was diffuse, robust nuclear positivity for SF-1, a sex cord-stromal marker, which superseded the misleading focal expression of myogenic markers. According to the report’s diagnostic highlight, the tumor closely mimicked a primary leiomyosarcoma, and diagnostic precision was achieved through the identification of biphasic architecture in the surgical specimen combined with the SF-1 result.

Following the revised diagnosis, the patient underwent five cycles of chemotherapy with paclitaxel and carboplatin. At the six-month follow-up, she remained free of recurrence, the report states.

The authors emphasize that this case underscores the critical importance of including Sertoli-Leydig cell tumor in the differential diagnosis of pelvic spindle cell tumors. They argue that using a comprehensive immunohistochemical panel that incorporates sex cord-stromal markers is imperative to avoid diagnostic inaccuracies and to facilitate appropriate clinical management.

As a single case report, the findings describe one patient’s diagnostic course and do not establish general treatment outcomes. The article was published as an open access case report and shared early as a peer-reviewed, accepted version subject to further edits before the final Version of Record.

Subject of Research: Diagnostic challenge of an ovarian Sertoli-Leydig cell tumor with smooth muscle differentiation mimicking leiomyosarcoma

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

Article References: Lin, C., Deng, P., & Fan, L. (2026). Poorly differentiated ovarian Sertoli-Leydig cell tumor with smooth muscle differentiation masquerading as leiomyosarcoma: a case report. Discover Oncology. https://doi.org/10.1007/s12672-026-06186-4

Image Credits: AI Generated

DOI: 10.1007/s12672-026-06186-4

Keywords: Sertoli-Leydig cell tumor, ovarian tumor, leiomyosarcoma, case report, immunohistochemistry, SF-1, smooth muscle differentiation, sex cord-stromal tumor, pelvic spindle cell tumor, differential diagnosis, Discover Oncology, gynecologic pathology