[Radiological differential diagnosis of colorectal cancer]

This study was undertaken to evaluate the radiological diagnosis of colorectal polypoid lesions between 0.6 cm and 3.0 cm in size. Lesions less than 0.6 cm were mostly benign or, on rare occasions, early carcinomas limited to the mucosa. Lesions more than 3.0 cm in size were mostly advanced carcinomas. Lesions were classified by modified Maruyama's classifications as follows, type "a" (lesion with long stalk), type "b" (lesion with short or sessile lesion), type "c" (plaque-like lesion), type "d" (lesion with central depression) and type "e" (the others). Type "a" lesions were either benign or early cancers but these could not be distinguished radiologically. Type "b" and "c" lesions more than 1.0 cm in size and with indentation of colonic wall, had a great probability of being early cancer. Type "d" lesions with a slight depression were either benign or early cancers but type "d" lesion with a moderate depression were all advanced cancers. Type "e" lesions were mostly villous tumors so that it was difficult to diagnose whether these were cancer or not.