The radiologial diagnosis of early carcinoma of the large bowel resolves itself into the following six points.
1. Detailed analysis of macroscopical characteristics is of no use for the radiological differential diagnosis of polypoid lesions of the large bowel.
2. It is the most important procedure first to distinguish whether a polypoid lesion is pedunculated or sessile, and, then, whether it has central depression or not, when the lesion is sessile.
3. It is impossible to decide radiologically whether a pedunculated lesion is benign or early carcinoma. There is no advanced carcinoma in pedunculated lesions.
4. A sessile lesion within 1.0 cm in the largest diameter and without central depression is most probably diagnosed as early carcinoma.
5. A sessile lesion with central depression should be diagnosed as advanced carcinoma, Borrmann Type II, rather than eatly carcinoma, Type IIa+IIc, regardless of its size. There is no benignancy in the lesions with central depression.
6. It is very difficult to decide invasion depth of carcinoma by the extent of depressed sign (deformity) of the bowel wall, although early carcinoma reveals generally a slight sign of it.