Endometrial stromal sarcoma arising from endometriosis of the terminal ileum: the role of immunohistochemistry in the differential diagnosis

Abstract

Low-grade endometrial stromal sarcoma (LESS) is an uncommon uterine malignancy. Occasionally, it may develop in extrauterine endometriotic lesions and present morphological characteristics mimicking various neoplasms, making its diagnosis very challenging. We report a rare case of a 56-year-old woman presenting with a pelvic mass, initially presumed to be of ovarian origin. After surgical excision the diagnosis of a LESS arising from foci of endometriosis of the terminal ileum was established. Pelvic lymph nodes and omentum were also infiltrated. The patient received adjuvant chemotherapy and medroxyprogesterone; she is alive with no evidence of disease after a follow-up of 38 months. Immunohistochemical characteristics of the tumor are very important for the differential diagnosis of this rare neoplasm and include diffuse strong positivity for CD 10, estrogen receptor expression and CD 34 negativity.