We report a rare case of a 46-year-old woman developing endometrial stromal sarcoma (ESS) on the grounds of extrauterine endometriosis. The patient presented with symptoms of stenosis of the rectosygmoid colon. The tissue samples were submitted to histological and immunohistochemical analyses using antibodies for indirect staining. The trial showed multiple foci of endometriosis and mesenchymal malignant tissue described as ESS in the bowel wall, mesentery and in the remnants of the left adnexae. According to our findings, we suspect that ESS might have arisen in colon endometriosis.