Immunohistochemical Expression of Ki67 and p53 in Primary Breast Carcinoma and Combined Ki67-p53 Status Phenotypes in Hormone Receptor Positive Breast Carcinoma

introduction: The conventional lmmunohistochemical (WIC) biomarkers used to assess breast cancer patients include Hormone Receptor (HR) status and HER2 status, IHC analysis of Ki67 is useful to stratify the HR-positive tumours into good and bad prognosis categories; p53-status can identify patients likely.to respond to chemotherapy. Aim: To evaluate the IHC status of Ki67 and p53 in invasive primary breast carcinoma and to assess their relationship with HR status, HER2 status and clinicopathologic factors. Materials and Methods: This observational study conducted between August 2014 to April 2016 included fifty patients with invasive primary breast carcinoma comprising 48 ductal carcinoma, No Special Type (NST) and two mucinous carcinoma cases. Patients treated with neoadjuvant therapy were excluded from the study, The IHC analyses for ER, PR, HER2, Ki67 and p53 status were done on paraffin-embedded tissue sections. The Ki67 and p53 statuses were correlated with the clinicopathological parameters and ER, PR, HER2 status. Based on their IHC profiles, the tumours were classified into clinically defined treatment oriented subtypes. The association between the clinicopathological parameters and positivity of IHC biomarkers were analysed using Chi-square test and Fisher's-exact test. The p-value was calculated to ascertain a statistical significance. Results:The 50 cases analysed comprised 54% postmenopausal and 46% premenopausal patients. Luminal cancers constituted 46% followed by 30% HER2- like and 24% basal-like tumours. Molecular subtypes showed significant correlation with age, menopausal status, and histologic grade. Ki-67 showed significant correlation with grade, HER2 status and molecular subtypes. p53 showed significant correlation with menopausal status and nodal status. The combined Ki67-p53 status showed a significant correlation with menopausal status, grade, nodal status and HER2 status of the HR-positive tumours. Conclusion:The inclusion of Ki67 in the routine breast IHC panel, facilitates the subtyping of breast cancers into therapy oriented surrogate molecular subtypes. Further, when compared to Ki67 alone, the Ki67-p53 combination will provide even better costeffective, predictive and prognostic information for the routine clinical management of breast cancers, especially for the HR positive tumours.