Background: Breast cancer is one of the leading cancer affecting women in India. An early diagnosis has a great significance especially since it carries a high morbidity and mortality rate. It is common among women in both developed and developing countries. Objectives: The present study was carried out to determine the histopathological and immunohistochemical pattern of invasive ductal carcinoma breast in a tertiary care institute. Methodology: 1418 cases of breast cancer diagnosed as invasive ductal carcinoma (IDC) were studied in the department of pathology of a teaching hospital. Estrogen receptor (ER), Progesterone receptor(PR) and Her-2/Neu expression were assessed using immunohistochemical staining and correlated with other prognostic factors including age, tumour size, grade and histomorphological type. Study Area: The study was carried out in the department of histopathology of a tertiary care institute in northern India. Study Design: Formalin fixed paraffin embedded paraffin blocks were analysed. The study duration was 9 years (January 2011 – December 2018). Statistical Analysis: The results were analyzed using SPSS statistical package version 26.

Keywords: Carcinoma; Breast; Mastectomy; IHC; ER; PR; Her-2/Neu; Prognosis.