RESUMO
BACKGROUND: Molecular subtypes play an important role in predicting prognosis and guiding treatment for breast cancer. Having a better knowledge of ethnic molecular features is essential. OBJECTIVES: Determining the distribution of various breast cancer molecular subtypes and investigating the relationship between these subtypes and clinicopathological features. METHODS: Retrospective data was collected from Hanoi National Cancer Hospital and Bach Mai Hospital that included 274 women diagnosed with invasive breast cancer between January 2017 and June 2019. Patients were categorized into five subtypes according to the 2015 St. Gallen molecular classification. The variables analyzed were molecular subtypes and tumor-related characteristics. To evaluate the relationship between these subtypes and clinicopathological features, a Chi-squared test and Fisher exact test were performed. RESULTS: The most prominent subtype was Luminal A (33.2%), followed by Luminal B/Her2- (19.7%) and Luminal B/Her2 + (17.5%), then HER2 overexpression (16.4%), whereas triple negative was the least popular subtype (13.1%). Particularly, 33.9% of all patients, including the Luminal B/Her2 + and the HER2 overexpressing groups, were Her2 positive. There was a statistically significant difference between molecular subtypes and histological type (p = 0.01), tumor grade (p < 0.001), but it was independent of age, tumor size, lymph node metastasis, and lymphovascular invasion. CONCLUSIONS: In contrast to the triple negative variant, the Luminal A variant is the most common among Vietnamese women. The rate of positive tests for HER2 was rather high. These subtypes were closely related to tumor grade and histopathological type. Understanding the molecular subtypes and their relation to clinicopathological features helps clinicians with patient treatment, and prognosis. The application of the 2015 St. Gallen molecular classification should be recommended for use in clinical practice.