Endometrial stromal sarcoma presenting as a cystic abdominal mass

Endometrial stromal sarcoma (ESS) is rarely localized in extrauterine sites if metastasis or local extension of the primary uterine tumour are excluded, and diagnosis can be delayed because of the unusual site. We report a case of abdominal ESS in a 45-year-old woman who presented with an abdominal complaint. Ultrasound of the abdomen showed a large multiloculated cystic mass. The complete excision of the tumour revealed ESS arising in endometriosis. The tumour expressed hormonal receptors and the patient was administered hormonal therapy. ESS has a better prognosis than the sarcoma that is part of differential diagnosis, and is associated with endometriosis in about one-half of cases.