Evaluation of Ki-67 Proliferation Index in Breast Cancer Subtypes and Its Correlation with Various Histopathological and Other Prognostic Parameters

Background: The current classification of breast cancer is based on molecular markers. However, due to the unavailability of these markers in all healthcare institutes in developing countries like India, certain IHC markers such as ER, PR, HER2Neu, and Ki67 act as surrogate markers and play a crucial role in determining prognosis and targeted therapy for each patient. This study aims to evaluate Ki67 expression in breast carcinomas and its correlation with IHC status and other prognostic parameters of the tumor. Materials and Methods: The study was conducted on 200 specimens of breast carcinoma cases received in the Pathology Department over a period of 18 months at RNTMC and MB Hospital, Udaipur. These specimens were processed and examined under a microscope to describe them in terms of histologic subtype, lymph node status, and histologic grade. IHC status of ER, PR, HER2Neu, and Ki67 was evaluated. Results: The mean age of presentation was 48.3 years. The most common histologic subtype was Invasive Breast Carcinoma (NOS) (81%), and the IHC-based subtype was Luminal-A (54%). The most common histologic grade was Grade II (55%). High Ki67 expression was observed in many cases of Luminal-B, HER2neu-enriched, and triple-negative types of breast carcinoma. Low Ki67 expression was seen in the Luminal-A subtype. There is a significant correlation between tumor size, lymph node positivity, histologic grade, ER, PR, and HER2Neu status with Ki67 expression. Conclusion: Ki67 is a significant biomarker of breast cancer because higher Ki67 correlates with higher tumor grade. Therefore, its evaluation, along with other IHC markers, can aid in the targeted treatment of the patient.