Context: The classification of breast cancers into subgroups on the basis of gene expression patterns is often regarded as the gold standard, but its use remains limited due to the expense involved. Consequently there is interest in using Immunohistochemical (IHC) markers to classify tumors into subtypes that are surrogates for those based on geneexpression profiling. Aims: To classify molecular subtypes of breast carcinomas based on the surrogate IHC markers and to evaluate the correlation between these subtypes and other clinical parameters Settings and Design: The study was done from January 2014 to June 2016 on 70 cases of modified radical mastectomy specimens diagnosed as invasive breast cancer on histopathological examination. Methods and Material: The Immunohistochemical evaluation of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2/neu) were done on formalin fixed paraffin embedded tissue sections and are compared with the age of the patients, histological grade and tumor stage. Statistical analysis used: Analysis of variance for continuous variables and chisquare test for categorical variables. Results: The surrogate classification consisted of 36 cases of luminal A, 16 cases of luminal B, 13 cases of triple negative/basallike tumors and 05 cases of HER2/neu subtype. The subjects of luminal A subtype were older, had a well/ moderately differentiated histological grade, presented with small tumor size, less number of lymph nodal metastasis and had Early stage breast cancer. Subjects with triple negative tumors were younger, had moderately/ poorly differentiated histological grade, presented with large tumor size, high lymph nodal metastasis and advanced stage breast cancer. Conclusions: IHC markers of breast cancer can be used as surrogate markers for molecular classification and are comparable with other prognostic markers.

Keywords: Breast Carcinoma; Immunohistochemical Markers; Molecular Classification; Progesterone Receptor; Estrogen Receptor.