ABSTRACT
BACKGROUND: Endometrial stromal sarcoma arising from extrauterine endometriosis is a rare and not easily diagnosed tumor. We present a case arising from sciatic nerve endometriosis in a 50-year-old woman. CASE: The patient had a long history of endometriosis and presented with a left buttock mass and motor deficit. Magnetic resonance imaging showed a large tumor of the sciatic nerve with pelvic extension. She underwent total hysterectomy, bilateral salpingo-oophorectomy, and excision of pelvic endometriotic pockets, allowing the diagnosis of low-grade endometrial stromal sarcoma arising from endometriosis. She received systemic chemotherapy, gonadotropin-releasing hormone agonist therapy, and palliative radiation therapy, but her disease progressed. CONCLUSION: Aggressive endometriosis raises important diagnostic and therapeutic difficulties and may correspond to misdiagnosed rare malignant neoplasms, which should be treated.
