Colorectal cancer (CRC) remains a leading cause of cancer-related mortality worldwide. Colonic polyps are known to be potential precursors to CRC. Evaluating cellular proliferative activity across various polyp types and normal mucosa is essential for understanding the early stages of colorectal carcinogenesis. Ki-67 expression serves as a reliable biomarker of proliferative activity.

Aim. To investigate Ki-67 expression patterns in the epithelial and stromal cells of tubular adenomas and hyperplastic polyps of the distal colon.

Materials and methods. Pathohistological and immunohistochemical (IHC) analyses were performed on biopsy specimens from 139 patients (age range: 22–81 years). The cohort included 68 patients with tubular adenomas of the distal colon, 56 with hyperplastic polyps, and 15 controls (age range: 22–72 years) with normal distal colonic mucosa.

Results. Distal colonic polyps were characterized by moderate epithelial cell proliferation (Me = 61.38 % (49.28; 70.38) for tubular adenomas; Me = 35.26 % (4.37; 45.23) for hyperplastic polyps) and low level of stromal cell proliferation (Me = 10.51 % (1.08; 15.57) for tubular adenomas; Me = 2.84 % (0.70; 5.45) for hyperplastic polyps). Direct correlations were observed between the degree of dysplasia and Ki-67 expression levels in both epithelial (γ = 0.79) and stromal cells (γ = 0.61). The spatial distribution of Ki-67-positive cells demonstrated distinct patterns: in normal mucosa and hyperplastic polyps, proliferation was primarily confined to the lower and middle thirds of the crypts. In contrast, tubular adenomas with low-grade dysplasia exhibited an even distribution, while those with high-grade dysplasia showed a predominant localization in the upper and middle thirds of the crypts.

Conclusions. The findings indicate that evaluating Ki-67 expression in both the epithelial and stromal compartments of distal colonic polyps is a valuable tool for assessing malignancy risk. This marker may serve as a supplementary pathohistological criterion for the evaluation of precancerous lesions.