Study of hormone receptor status and HER/2-neu expression in breast malignancies and its implication in molecular subtyping in a tertiary care hospital

Background: Breast cancer has ranked number one cancer among Indian females. In addition to conventional histopathology based on morphology, the College of American Pathologists (CAP) and American Society of Clinical Oncology (ASCO) recommend evaluation of hormone receptors – Estrogen Receptor (ER), Progesterone Receptor (PR) as well as HER2. The role of hormone receptors as a prognostic and therapeutic tool in breast cancer is widely accepted. The molecular subtyping is formulated by immunohistochemical characterization as well as gene expression profiling though the latter is currently not feasible. In the present study we retrospectively measured the frequency of hormone receptor and HER2 positivity in breast cancer patients and classified into the molecular subtypes. Materials and Methods: We conducted a three year retrospective study on 45 cases of breast cancer who underwent Modified radical mastectomy (MRM), subjected to immunohistochemical evaluation for the status of hormone receptors and HER2 expression as per the ASCO/CAP guidelines. In addition, the clinical details pertaining to patient age, sex, tumour size and histological type were recorded. The molecular subtype of each case was determined and the prevalence compared with similar studies in literature. Results: The predominant histopathological type in this study was Invasive ductal carcinoma (93.3%). Immunohistochemistry for hormone receptor status revealed ER positivity of 55.5%, PR positivity of 46.6% and HER2 positivity of 33.5%. Among molecular subtyping Luminal A attributed to 33.3% of the cases and was the most prevalent followed by HER2 enriched with 26.6%. Conclusion: The combined utility of conventional histopathology coupled with immunohistochemical assay based molecular subtyping for routine clinical practice enables diagnosis, estimating prognosis and predicting response to treatment. Keywords: Breast cancer, Immunohistochemistry, Hormone receptors, HER/2-neu, Molecular subtype.