The Relationship of Ki-67 Over-expression with Clinicopathological Prognostic Parameters in Invasive Breast Carcinomas

OBJECTIVE Immunohistochemical Ki-67 index is a useful method to determine the prognosis. We aimed to evaluate the association of Ki-67 score, using 14% and 20% cut-off values, with clinicopathological parameters in invasive breast carcinomas. METHODS Pathology reports of 162 females were retrospectively reviewed and parameters including age, menopausal status, multifocality/multicentricity (MF/MC), tumor size, histological type, grade, lymphovascular invasion (LVI), perineural invasion, axillary lymph node status, ER, PR, HER2 status, Ki-67 index, and molecular subtype were recorded. The cases were grouped according to two separate Ki-67 cut-off values (high: >= 14% and >= 20%, low <14%, and <20%). Ki-67 score was compared with other clinico-pathological parameters statistically using Chi-square test. RESULTS When the Ki-67 score was grouped according to 14% or 20% cut-off values, it was found to be associated with similar clinicopathological parameters. There was a significant correlation between high Ki-67 score and high grade (p<0.001, p<0.001), LVI (p=0.002, p=0.022), ER negativity (p=0.001, p<0.001). When ER expression was grouped as negative, low positive and positive, similar results were obtained (p=0.003, p=0.001). There was a significant association between Ki-67 score and molecular subtypes (p<0.001, p<0.001): Ki-67 score was higher in cases that belong to Luminal B subtype and lower in cases that belong to Luminal A in comparison to others. Ki-67 score had no association with age, menopausal status, MF/MC, tumor size, perineural invasion, axillary lymph node involvement, PR, and HER2 status. CONCLUSION Standardization of interpretation of Ki-67 proliferative index and cut-off value for scoring will improve the demonstration of the prognostic signification of Ki-67 in invasive breast carcinomas.