Malignant polyps are adenomatous polyps that contain cancerous cells that have penetrated the muscularis mucosae. Pedunculated malignant polyps that have not yet developed to level 4 invasion and have no other adverse histopathologic criteria have a high likelihood of cure by endoscopic excision alone. However, if level 4 invasion has been reached or if any additional adverse characteristic, such as poor differentiation, lymphatic or venous invasion, or close or involved margins, is present, the risk of inadequate treatment from endoscopic excision alone becomes appreciable. Under such circumstances, a definitive resection is favored unless the increased risk of recurrence is offset by age-related limited life expectancy or substantial comorbidities. Sessile malignant polyps are more likely to demonstrate level 4 invasion. In addition, these lesions are often less satisfactorily treated by endoscopic excision. In most circumstances, unless patient factors contraindicate intervention, resection should be performed.