Prevalence and clinicopathological features of human epidermal growth factor receptor-2–low breast cancers: A single-center experience

ObjectiveHuman epidermal growth factor receptor-2-low breast cancer, characterized by low-level human epidermal growth factor receptor-2 expression and immunohistochemistry score 1+ or immunohistochemistry score 2+ without amplification, has been proposed as a distinct subgroup. This study investigated the prevalence and clinicopathological characteristics of human epidermal growth factor receptor-2-low breast cancers.MethodsA retrospective observational cohort study was conducted on patients diagnosed with invasive breast carcinoma between 2021 and 2023 at a single tertiary center. Data on histological type, tumor grade, human epidermal growth factor receptor-2 status, and Ki-67 proliferation index were collected.ResultsAmong the 181 patients who were included, 54.7% were classified as human epidermal growth factor receptor-2-low, 27.6% as human epidermal growth factor receptor-2-negative, and 17.7% as human epidermal growth factor receptor-2-positive. Human epidermal growth factor receptor-2-low tumors were predominantly those classified into grade 2 (69.7%). The mean age of patients with human epidermal growth factor receptor-2-low tumors was 60 years. The Ki-67 index was significantly lower in human epidermal growth factor receptor-2-low tumors than in human epidermal growth factor receptor-2-positive and human epidermal growth factor receptor-2-negative groups (p = 0.001). No significant differences were observed in the rates of axillary lymph node metastasis among the groups (p = 0.13).ConclusionHuman epidermal growth factor receptor-2-low breast cancers constitute a significant proportion of breast cancer cases and are associated with distinct clinicopathological features, including high estrogen reception positivity and lower Ki-67 proliferation rates.