Endometrial stromal sarcoma of the rectosigmoid colon arising in extragonadal endometriosis and revealed by portal vein thrombosis

Malignant transformation is an infrequent complication of endometriosis. Th e ovary is the primary site in 76% of cases, and extragonadal sites are ide ntified in 24%. Endometrioid carcinoma is the most common histologic type; sarcoma is very rare. We report a case of low-grade endometrial stromal sar coma of the rectosigmoid colon presenting with epigastric pain due to porta l vein thrombosis. This tumor arose from extragonadal endometriosis in a 61 -year-old woman and was treated by surgical resection. The main differentia l diagnosis of this unusual colonic neoplasm includes primary mesenchymal t umors, such as gastrointestinal stromal tumors.