Postoperative pathology of colonic leiomyosarcoma is highly likely to be a benign tumor, but a malignant smooth muscle sarcoma cannot be excluded. Colonic leiomyosarcoma is a smooth muscle tumor that occurs in the muscular layer of the colon and is very rare clinically. Smaller colonic smooth muscle tumors are not easy to detect, and larger colonic leiomyosarcomas can be detected as submucosal bulges in the colon during colonoscopy, because colonic leiomyosarcomas occur in the muscular layer of the colon, and the mucosal layer is usually intact, so it is more difficult to obtain a pathology, and direct surgical resection is often required to clarify the pathology. The pathology of this type of colonic tumor is usually a benign lesion, i.e., colonic smooth muscle tumor, with a better prognosis; very rarely, it may be a malignant smooth muscle sarcoma, and if so, the prognosis is extremely poor.