Background: Breast cancer is the most common type of cancer in women with increasing incidence in India. Infiltrating ductal carcinoma is the most common type of breast carcinoma amongst various histological entities. Immunohistochemical markers of prognosis and predictors for therapy include estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2/neu). Immunohistochemistry was used to evaluate how ER, PR, and HER2/neu were expressed in invasive ductal carcinomas of the breast. The objective was to study the correlation of these markers with one other and to various parameters like the patient's age, the tumor size, histological grading, and its spread to axillary lymph nodes.