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Published on: December 5, 2017
Integrated Histopathological and Molecular Classification of Breast Cancer Using Immunohistochemistry (ER, PR, HER2)
Farah Fatima Abbas1, Saba Kamil1, Nehad Khan1
1Department of Pathology, Dow International Medical College (DIMC), Dow University of Health Sciences, Karachi, Pakistan.
Introduction:
Molecular classification of breast cancer based on Estrogen Receptor (ER), Progesterone Receptor (PR), and Human Epidermal growth factor Receptor-2 (HER2) expression has improved therapeutic decision-making; however, accurate differentiation between luminal subtypes remains challenging. The Ki-67 proliferation index is a valuable biomarker for assessing tumor aggressiveness and guiding treatment strategies. This study aimed to determine the frequency of molecular subtypes in breast cancer biopsies and evaluate their association with clinicopathologic parameters.
Methodology:
A cross-sectional study was conducted at the Histopathology Section of the Dow Diagnostic Research and Referral Laboratory (DDRRL), Dow University of Health Sciences (DUHS), Karachi, from January to December 2024. A total of 913 breast cancer biopsy specimens were analyzed using immunohistochemistry for ER, PR, HER2, and Ki-67. Tumors were classified into Luminal A, Luminal B, HER2- enriched, and Triple-Negative Breast Cancer (TNBC). Ethical approval was obtained from the DUHS Institutional Review Board (IRB-3423/DUHS/Approval/2024/93).
Results:
Among 913 patients, middle-aged adults [41-60 years] were most commonly affected. Luminal A [41%] was the predominant subtype, and invasive ductal carcinoma was the most frequent histological pattern. Molecular subtypes showed significant associations with tumor grade, histology, and laterality, with TNBC exhibiting a higher frequency of Grade III tumors.
Discussion:
Luminal A tumors were predominantly Grade II and hormone receptor- positive, whereas TNBC demonstrated higher grades and aggressive behavior. An inverse relationship between ER/PR and HER2 expression was observed. High Ki-67 index correlated with higher tumor grade and ER/PR negativity.
Conclusion:
Combined histopathological and molecular classification provides important prognostic information and supports individualized breast cancer management.
