Level of carcinoma involvement in malignant polyps—pedunculated versus sessile adenomas. When carcinomatous cells are contained within the mucosa, without breaching the muscularis mucosae, the lesions are known as noninvasive carcinomas—severe focal atypia and intramucosal carcinoma (N). Once cancer has invaded through the muscularis mucosae into the submucosa of the bowel wall, the polyp is then termed a malignant polyp. Because lymphatics are present in the submucosa, metastatic spread is then possible. Increasing levels of invasion of the carcinoma, to the head (1), neck (2), stalk (3), and base of the stalk–submucosa (4), may carry worsening prognostic implications. A malignant sessile adenoma has, by definition, invaded the submucosa of the bowel wall (4). Noninvasive carcinomas (N) require no additional therapy after polypectomy. Usually, malignant polyps with invasions only of the head, neck, and stalk (1, 2, 3) and with clear resection margins and no poor prognostic features (see Table 88-7) are adequately treated by polypectomy alone. In malignant polyps with invasion of the submucosa of the bowel wall (4) or with poor prognostic features, colectomy should be seriously considered for potential cure.