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. The ovary is the primary site in 76% of cases, and extragonadal sites are identified in 24%. Endometrioid carcinoma is the most common histologic type; sarcoma is very rare. We report a case of low-grade endometrial stromal sarcoma of the rectosigmoid colon presenting with epigastric pain due to portal vein thrombosis. This tumor arose from extragonadal endometriosis in a 61-year-old woman and was treated by surgical resection. The main differential diagnosis of this unusual colonic neoplasm includes primary mesenchymal tumors, such as gastrointestinal stromal tumors.