Molecular Subtypes of Breast Carcinoma and Their Association with Clinicopathological Features

Background: Breast cancer is categorized into four primary molecular subtypes based on gene expression profiles and hormone receptor status: Luminal A & B subtypes, Basal-like, and HER2-enriched. This study assessed the association of molecular categories of breast carcinoma with the clinicopathological features. Methods: A cross-sectional study was conducted between January 2022 and August 2024; 200 mastectomy specimens were collected with a non-probability consecutive sampling technique from Ziauddin Hospital Histopathology Department in Karachi, Pakistan. Immunohistochemical analysis was done for ER, PR, HER 2 Neu, and Ki-67 and the findings were statistically analyzed for association with clinicopathological parameters. Results: Luminal B subtype was found to be the most common subtype. The study identified pT2 and pT3 as the most frequent pathological stages, with 74 cases (38.1%) and 71 cases (34.4%), respectively. Low-grade tumors were less frequent as compared to intermediate and high-grade tumors with 11 (5.5%), 73(36.5%), and 116 cases (58.0%), respectively. A significant association was observed between molecular subtypes and tumor grade, stage, and histological subtypes. However, insignificant association was seen with age, laterality, and tumor site. Conclusion: Luminal B tumor was the most frequent subtype, while luminal A was the least prevalent. Luminal B tumors were primarily associated with invasive ductal carcinoma invasive ductal carcinoma (NOS). These tumors were commonly found in women aged 41-50. Furthermore, a strong association of molecular subtypes was observed with histological grading and staging.