Radiologic diagnosis of invasive carcinoma on adenomatous polyps of the colon

The radiographic appearance at double contrast enema of 33 cases of invasive cancer on adenomatous polyps (AP) of the colon is reviewed. The radiologic diagnosis of malignancy was prospectively made in 54.5% of the cases. In 45.5% of the cases, malignancy was not suspected at the time of examination. The endoscopic appearance of these lesions was identical to that seen on the barium study. There are no radiologic criteria able to entirely rule out the possibility of a carcinomatous transformation of an AP. However, the radiologic features of malignancy (indentation of the intestinal wall and/or irregular outline of the surface of the polyp) have to be considered quite reliable.