Endometrial stromal sarcomas (ESS) in the female genital tract are uncommon and are usually of uterine origin.1,2,3 Extra-uterine ESS are extremely rare. Only 86 cases have been reported in the literature. 2,4 More than 50% of the cases were associated with pre-existing endometriosis. We report a case ofextrauterine low grade ESS associated with extensive endometriosis of the pelvis. We suspected that the tumor was a primary ovarian carcinoma due to elevated serum CA-125. Case ReportThe patient was a 45-year old premenopausal, multi-parous female (8 + 2). The patient presented with lower abdominal pain of 6 months duration associated with nausea and constipation.Her medical history included myomectomy for leiomyomas 17 years prior to this presentation. The patient was diabetic and hypertensive. Physical examination revealed a mass in the abdominal-pelvic region measuring 15 x 12 centimeters. Serum CA-125 was three times the normal range (197 mmol/L). Abdominal pelvic ultrasonography revealed an abdomino-pelvic mass of mixed echogenecity measuring 13x13 centimeters and located on the right side of the pelvis. The uterus was normal in size. A CT scan of the abdomen and pelvis showed a large heterogenouspelvi-abdominal mass with the epicenter in the region of the pelvic wall (Figure 1). The mass appeared adherent to the uterus and bowel wall. Laparotomy was performed and a mass adherent to the fundus of the uterus, the pelvic cul-de-sac and the bowel was found. There were multiple variable-sized nodules found in the wall of the pelvis, fallopian tubes and pelvic peritoneum. Total abdominal hysterectomy and bilateral salpingo-oophorectomy with debulking was performed. The patient was given progesterone therapy (Megace R ) and was discharged. Grossly the tumor was composed of multiple yellow-tan fleshy nodules with focal cystic areas. Focal areas of hemorrhage and necrosis were identified. The tumor was near the right adnexa. The uterus, fallopian tubes andovaries showed multiple tumor nodules. Microscopically, the tumor consisted of diffuse sheets of small closely packed cells with uniform round oval nuclei with coarse, evenly dispersed chromatin and small inconspicuous nucleoli. The cytoplasm was scanty and its boundaries were not well defined. A distinct vascular pattern was identified (Figure 2). This pattern was more prominent on the reticulin stain (Figure 3). Mitotic figures were less than 1 in 10 /high power field. No cellular atypia or pleomorphism were identified. The tumor was strongly positive for estrogen and progesterone receptors (Figure 4). Multiple deposits of the tumor were identified in the omentum. The ovaries and tubes showed multiple foci of tumor and endometriosis ( Figure 5). The endometrium showed cystic hyperplasia without evidence of ESS.