Immunohistochemical characteristics of Ki67 expression in premalignant lesions of the colon and rectum

Abstract

Introduction. According to the 2010 WHO classification, the precursors of colorectal cancer are conventional adenomas (tubular -AT, tubulo-villous - ATV and villous) and serrated lesions (hyperplastic polyps - HP, sessile serrated adenomas/polyps - SSA/P, traditional serrated adenomas - TSA). The evaluation of Ki67 expression is one of the components of the malignant potential of premalignant lesions of the colon and rectum. Materials and methods. Immunohistochemical expression of Ki67 was assessed in 28 HP, 30 SSA/P, 15 TSA, 30 AT, 28 ATV. In all cases the average percentage and location of colored nuclei were estimated. Results. Ki67 expression in HP and SSA/P was predominantly registered in the lower crypt regions, the Ki67-index in HP was 63%, in the non-dilated crypts of SSA/P - 66,2% (p>0,05). In the dilated crypts of SSA/P the Ki67-index was 35,8%, that is significantly lower than in the HP and the non-dilated crypts of SSA/P (p<0,05). In AT, ATV and TSA, the expression of Ki67 is noted predominantly in the upper crypt regions and is 59,3%, 64,2% and 63%, respectively (p>0,05). In the ectopic crypts of TSA the Ki67-index is 29,9% and is not significantly different from the basal regions in ATV. Conclusion. The predominance of Ki67-positive cells in the upper half of the crypts supports the "descending" model of cancer development in AT, ATV and TSA; the predominance of Ki67-positive cells in the lower half of the crypts in HP and SSA/P may be indicative of the "ascending" model of carcinogenesis. Based on the predominant localization of Ki67-positive cells and the index of proliferative activity, it is possible to divide the premalignant lesions of the colon and rectum into two groups: serrated lesions (HP + SSA/P) and conventional adenomas (AT + ATV + TSA).