Mullerian carcinosarcoma in the colon of a patient with history of endometrial carcinoma: A case report and insight into possible pathogenesis

•Mullerian carcinosarcoma can occur in extragenital sites.•Malignant transformation of endometriosis is common in the rectosigmoid area.•MLH1 hypermethylation has been implicated in endometriosis-associated carcinomas.•Adequate sampling is essential in determining the etiology of colonic tumors.