Subtyping of Breast Carcinoma According to ER/PR and HER2/neu Expression: A Cross-Sectional Study from Southern Part of Assam, India
Authors: Kanoo Bandana , Agarwal Sristi , Deka Monoj Kumar , Das Arindam 
Published: May 2024

Introduction: Globally, breast carcinoma is the most prevalent and lethal form of cancer in women. Breast cancer is no longer considered a single disease but a complex heterogeneous disease with multiple genetic and epigenetic alterations. The prognosis and management of the disease depend on histological stage, type, grade, tumour size, lymph node status, and the status of hormonal receptors like ER, PR, and Her2/ neu. Recently, more attention has been given to the molecular classification of breast cancer. Aim: To analyse and compare the clinicopathological characteristics of invasive breast cancer in the four breast carcinoma subtypes defined by the immunohistochemical expression of Estrogen Receptor (ER), Progesterone Receptor (PR), and Human Epidermal Growth Factor Receptor 2 (Her2/neu). Materials and Methods: The cross-sectional study was conducted on 64 primary invasive breast carcinoma cases diagnosed on mastectomy specimens between February 1, 2018, and July 30, 2022, in the Department of Pathology at the histopathology section of Silchar Medical College and Hospital, Silchar, Assam, India. Age and tumour characteristics (morphology, grade, stage, and size) and nodal disease status were included in the data for analysis. Immunohistochemical markers were analysed on the sections of these diagnosed cases. IBM Statistical Packages for Social Sciences (SPSS) software was used for data analysis. Qualitative data was presented as frequency and percentage, while quantitative data was presented as mean ±{Standard Deviation (SD)}. The Chi- square test was used to determine the statistical significance of hormonal receptors with the various clinicopathological features. A p-value of <0.05 was considered statistically significant. Results: In present study of 64 cases of invasive breast carcinoma, the mean age of patients was 51.95±12.72 years. Subtyping was performed based on hormonal receptors. Authors found that the Luminal A variety 33 (51.6%) was the most common hormonal subtype in present study, followed by the basal subtype 24 (37.5%). The Luminal A subtype was found to be predominant among others. The majority of the patients (59.4%) had stage-I tumours, and Ductal type carcinoma was the most common (57.8%). Histologically, most of the tumours were poorly differentiated (28, 43.8%), and most were sized ≤2 cm (41, 64.1%). Lymph nodes were not palpable in most of the patients (43, 67.2%). Subtype comparison with respect to age, stage, histological grade, type, size, and nodal status revealed statistically significant outcomes (p-value of <0.05). Conclusion: Classification based on Immunohistochemistry (IHC) provides prognostic and therapeutic information that cannot be obtained from either ER/PR or Her2/Neu status alone. The present study provides the incidence of different molecular subtypes in the southern region of Assam, and comparison among them with statistical correlation offers improved and crucial treatment guidance. IHC classification as a clinical tool for ER/PR and Her2/Neu testing is widely accessible, reasonably priced, based on immunophenotype/biologic phenotype categorisation of breast cancer, and is prognostic as well as partly predictive and needs to be practiced invariably.