Comparative Analysis of Ki-67 Proliferation Index in Colorectal Adenomas and Adenocarcinomas: An Immunohistochemical Study

Introduction: Colorectal carcinoma (CRC) is one of the most common cancers in various parts of the world. The evolution of CRC follows a stepwise genetic acquisition of mutations and a resultant transition from normal mucosa to adenoma and, ultimately, adenocarcinoma. The goal of the study was to assess the different immunohistomorphologic characters in adenomas and adenocarcinomas using the Ki-67 tumor proliferation marker that may have diagnostic or prognostic relevance. Materials and methods: This descriptive study was conducted on 40 paraffin-embedded tissue blocks collected from the colorectal tissues in a tertiary care hospital in Chennai, Southern India. Ki-67 proliferation index (PI) was analyzed by immunohistochemically stained slides by a set of two pathologists to eradicate bias. Results: Tissue samples from 25 (62.5%) male and 15 (37.5%) female patients with a mean age of 56.9 ± 16.09 (age range six to 83 years) and a median age of 60 years were included in the study. Adenocarcinomas comprised 24 (60%), whereas 16 (40%) cases were adenomas. There was a significant mean difference between adenomas (Mean PI = 30.97 ± 11.44) and adenocarcinomas (Mean PI = 46.33 ± 25.16) when compared with Ki-67 PI (%), with a p-value = 0.02 (< 0.05). Conclusions: The Ki-67 immunohistochemical technique is a simple and reproducible technique. A gradual increase in expression of Ki-67 was observed from low-grade adenomas to high-grade adenomas and adenocarcinomas, which may serve as a routine tumor proliferation marker that can be routinely used as a diagnostic or prognostic marker in CRCs.