The radiographic features of small colon cancers.

The commonly accepted criteria for colon malignancy were investigated in malignant and benign polyps smaller than 3 cm in diameter. It was found that most small tumors, both benign and malignant, were sessile and smooth in outline. It was only when the polyps increased in size that their outlines became lobulated or irregular. A stalk was not seen in polyps smaller than 1 cm in diameter. Retraction at the base of a cancer was likewise not seen in these small lesions. The typical malignant characteristics became apparent only when the polyp had grown to 2 to 3 cm in diameter.