Molecular Subtyping of Carcinoma of the Female Breast in a Tertiary Teaching Hospital in Northern Nigeria

Abstract

Background: Cancer of the breast is globally the most common female cancer including in Nigeria. Newer treatment modalities are based on tumor immunophenotyping, thus the need to characterize these tumors among women with the disease in Northern Nigeria. Aims: This study aims to classify carcinomas of the breast diagnosed in the pathology laboratory of a teaching hospital based on their expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2/neu (HER2/neu) overexpression. Methodology: The histology slides of 478 carcinomas of the breast as well as the ER, PR, and HER2 immunohistochemistry records of 118 stained cases were retrieved and reviewed. Results: Age range of cases was from 20 to 80 years (mean = 46.9 ± 13). The most common histomorphologic entity was invasive carcinoma (NST) which accounted for 73.2% of cases. These were followed in frequency by invasive lobular carcinoma accounting for 6.8% of cases and invasive papillary carcinoma representing 6.5% of cases. Overall, 169 cases (37.6%) were Grade III tumors while Grades II and I tumors accounted for 35.1% and 27.3% of cases, respectively. Triple-negative tumors were the most common molecular subtype and comprised 46.6% of all cases. Luminal B (LUMB) was the least common and accounted for 8% of all cases. HER2 overexpression and LUMA were seen in 17.9% and 28.8% of cases, respectively. Conclusion: Carcinoma of the breast in the population studied occurs at a younger age than among Caucasians. The tumors are characterized by preponderance of invasive carcinoma (NST), high histological grade, and triple-negative phenotype.