Subtypes of Breast Cancer in Northern India-An Immunohistomolecular Subtypes of Invasive Breast Cancer

Introduction: Breast cancer is a heterogeneous disease that may differ in therapeutic response and prognosis despite similarities in histopathologic types, grade and stage. Molecular studies have identified distinct subtypes of breast carcinoma each having unique recognisable phenotypes and clinical outcomes. Aim: To study the histomorphological features and Immunohistochemical (IHC) profile of breast cancer, to study the distribution of molecular subclass, and to study the morphological features of different molecular subclasses and the association between the pathological features associated with adverse prognosis with the molecular subclass. Materials and Methods: Present study was a prospective cross-sectional observational study based on mastectomy specimens of 122 cases of consecutive cases of invasive breast cancer submitted over 1.71 years in Department of Pathology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India. On IHC staining with Estrogen Receptors (ER), Progesterone Receptors (PR), Human Epidermal growth factor Receptor 2 (HER2), Cytokeratin (CK5/6) and Epidermal Growth Factor Receptor (EGFR) these cases were classified into Luminal A, Luminal B, HER2 overexpression, basal like and normal breast like molecular subclass. All statistical analysis were performed using Statistical Package for the Social Sciences (SPSS) version 16 (SPSS, Inc., Chicago, IL, USA). Results: The proportion of each subytpes detected in present study were: Luminal A-28.69% (35), Luminal B-17.21% (21), HER2 over expressing-25.41% (31), Basal-Like Breast Carcinoma (BLBC)-26.23% (32) and the rest unclassified category (normal breast like)-2.46% (3). The following variables were significantly associated with molecular breast cancer subtypes. The tumours of BLBC and Her2 overexpressing were larger, poorly differentiated, higher mitotic index, more number of positive lymph nodes and with more geographic and central necrosis than Luminal A group. These features were statistically significant (p<0.05). Conclusion: Identification of molecular subtype of breast cancer is extremely important for predicting prognosis and therapeutic response of the breast cancers and thus has role in management of patients of breast cancers. BLBC is a molecular subtype of breast cancer known for its aggressive behaviour and poor prognosis is identified by expression of basal CKs.