Molecular Subtypes of Breast Cancer in Quetta - A Hospital-Based Study

Abstract

Objective: This study aimed to determine the molecular subtypes of breast cancer using
immunohistochemistry and to assess their distribution in the study population.
Study Design: It was a retrospective observational study.
Place and Duration of Study: The study was done at Combined Military Hospital, Quetta, from January 2022 to May 2025.
Materials and Methods: The study included 105 patients with complete histopathological data. The data was analysed using SPSS version 20, and employing chi-square tests to evaluate their associations. Statistical significance was determined at p-value < 0.05.
Results: Among the 105 cases, Invasive Ductal Carcinoma (IDC) was most common (89.5%, n=94), followed by Invasive Lobular Carcinoma (ILC) (4.8%, n=5) and Mucinous Carcinoma (3.8%, n=4). Rarer types included Metaplastic carcinoma and Medullary carcinomas. IHC-based molecular subtyping revealed Luminal A as the predominant subtype (40%, n=42), followed by Luminal B (24%, n=26), Triple-Negative Breast Cancers, TNBCs (19%, n=20), and HER2-enriched (16.2%, n=17). These subtypes were correlated with the patient's age,
histological grade, and proliferation index.
Conclusion: Luminal A emerged as the most common molecular subtype, typically presenting with a lower histological grade than Luminal B, HER2-enriched, and TNBCs. Most lobular carcinomas were Luminal A type. TNBCs were high-grade, more frequent in younger patients, while other subtypes were common in older age groups. Utilizing IHC markers for molecular subtyping can enhance prognosis and facilitate targeted therapies for improved patient outcomes.