Clinicopathological management of the patient with a malignant colorectal adenoma

A malignant adenoma of the colorectum is defined as an adenoma in which cancer has invaded by direct continuity through the muscularis mucosae into the submucosa [ 1]. The biological basement membrane of the colon is the muscularis mucosae. Thus the term 'cancer' cannot be applied to a neoplastic polyp which is confined to the mucosa and does not have the potential to metastases [ 2-4]. The term polypoid carcinoma is reserved for a polyp which is entirely replaced by carcinoma. There is however no practical benefit in distinguishing between the terms malignant adenoma and polypoid carcinoma [ 1, 4, 5]. The term carcinoma-in-situ is used by some to describe an adenoma containing severe dysplasia. Not having invaded through the muscularis mucosa, it is not a carcinoma. When the diagnosis of malignant polyp is presented by the clinician to the patient, a decision is needed as to whether the polypectomy on its own is sufficient therapy or whether the patient should be subjected to surgical resection. What are the pathological and clinical factors that contribute to this decision? This review examines the issues that require consideration to arrive at a balanced view of this difficult dilemma and to allow the patient to give informed consent to the management option decided upon.