A case of high-grade endometrial stromal sarcoma arising from endometriosis in the cul-de-sac

This report describes a rare case of high-grade endometrial stromal sarcoma (ESS) arising from pathologically confirmed endometriosis in the cul-de-sac. A 37-year-old woman presented with irregular menstruation, pelvic pain, and diarrhea. Magnetic resonance imaging and colon biopsy suggested endometriotic nodule of the cul-de-sac. The tumor size was reduced with hormonal therapy, and the residual tumor was excised, resulting in the pathologic diagnosis of endometriosis. Two years later, a soft mass reappeared with rapid growth. Tumor extraction was performed, and the histopathologic diagnosis was high-grade ESS. Neither hormonal therapy nor chemotherapy was effective, and the patient died 6 months postoperatively. ESS should be included in the differential diagnosis of malignant transformation of endometriosis.