Prevalence of non-polypoid colorectal neoplasms in southern Brazil

Several studies suggest that non-polypoid lesions (NPL) show higher aggressiveness than polypoid lesions, particularly depressed lesions. The present study aimed to assess the prevalence of NPL and the presence of advanced histology in a Brazilian population.

Two thousand and sixty-seven superficial neoplastic lesions diagnosed in 1135 patients were analyzed. Lesions were classified as polypoid and non-polypoid (flat and depressed) types, and evaluated for site, size, and histology (adenoma with grade of dysplasia, or early cancer).

Prevalence of NPL was 46.5%. NPL predominated in the right colon (62.9%), whereas polypoid lesions were detected mainly in the left colon (53.2%) (P < 0.001). NPL had a 34% higher probability of occurring in the right colon than polypoid lesions (P < 0.001). NPL were smaller than polypoid lesions (P = 0.03). There were 208 lesions >10 mm, of which 40 (19.2%) had advanced histology: 13% (18/138) of polypoid lesions; 27.3% (18/66) of flat lesions; and 100% (4/4) of depressed lesions (P < 0.001). Among 1859 neoplasms ≤10 mm, only 18 (1%) had advanced histology, and 15 of them were depressed lesions (P < 0.001). Advanced histology was more commonly detected in NPL than in polypoid lesions (P = 0.007), with significant difference in size (P < 0.001). NPL showed more advanced histology than polypoid lesions (OR 2.06; P = 0.01), especially depressed lesions (OR 36.35; P < 0.001). Among all neoplasms, the prevalence of depressed lesions was 2.2%.

NPL showed high prevalence and higher aggressiveness than polypoid lesions, especially the depressed type.