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Describe the current general classification of colon polyps. Which features of an adenomatous polyp correlate with greater malignant potential? Colorectal polyps are classified histologically as neoplastic or non-neoplastic (Table 1). The majority of polyps are small, non-neoplastic lesions that are found during screening or when procedures are performed for other diagnostic reasons (for example, a gastrointestinal bleed). The malignant potential and subsequent screening intervals are dependent on polyp type. All adenomas have variable degrees of dysplasia ranging from low-grade to highgrade. Classically, it is believed that the malignant potential of adenomas correlates with type of polyp, size, and degree of dysplasia. Higher grades of dysplasia, increasing percentage of villous tissue within the polyp, and polyps greater than 1 cm in diameter are associated with increased risk of malignancy. A polyp is considered malignant when cancer cells within the neoplasm have extended to the submucosa via penetration through the muscularis mucosal layer. The adenoma-carcinoma sequence has traditionally been characterized as a uniform progression from normal mucosa, to adenoma, to carcinoma through an underlying homogenous carcinogenic pathway. The process of adenoma development is initiated when both copies of the adenomatous polyposis coli (APC) tumor suppressor gene are deactivated in a single epithelial cell. The consequent lack of the suppressor permits activation of oncogenes, including, but not limited to, p53 and k-ras. There is evidence, however, that colorectal carcinogenesis is a heterogeneous process involving more than one precursor lesion.