High-grade Transformation in Adult Granulosa Cell Tumor: Potential Diagnostic Challenges and the Utility of Molecular Testing

Adult granulosa cell tumor (AGCT) is the most common sex cord-stromal tumor, accounting for about 1% of all ovarian tumors. It has a propensity for recurrences, especially late in the disease course. High-grade or sarcomatoid transformation has been rarely described in AGCT. We present a case of a 65 year old woman who presented with hemodynamic shock and bowel obstruction from a large pelvic mass. Histologic examination revealed predominantly high-grade epithelioid and spindled cells with high mitotic activity and necrosis. A minor component suggestive of AGCT was also identified. Molecular analysis confirmed the diagnosis of AGCT by revealing FOXL2 C134W mutations. Additionally, TP53 mutations were also detected which may contribute to the high-grade transformation. Our case is unique because the high-grade sarcomatous component constituted most of the tumor and the areas of "typical" AGCT were minor. Also, the clinical and operative findings did not suggest a specific site of origin leading to a broad differential diagnosis. High-grade transformation in AGCT is a rarely described phenomenon. The awareness of this presentation is helpful in reaching the correct diagnosis. Molecular analysis may be an extremely helpful adjunct in challenging cases.