Introduction: The molecular classification of breast cancer (BC) based on gene expression and then protein profile has made it possible to distinguish different molecular subtypes. The objective of this study was to describe immunohistochemical features of BC infiltrating women at the Nganda Hospital Center in Kinshasa, Democratic Republic of the Congo (DRC). Methods: A retrospective study from 2014 to 2019 involved 190 patients with invasive BC who were enrolled at the Nganda Hospital Center. The tumors were analyzed histologically and classified after an immunohistochemical study into subtypes: luminal A, luminal B, HER2-overexpressed, and triple-negative. A chi-square test was performed to assess the relationship between age, histological grade, and these subtypes. Results: The luminal A subtype (44.74%) was the most common, followed by luminal B (40.53%), triple-negative (10.53%), and HER2-overexpressed (4.20%). The mean age of the patients at diagnosis was 48.27 years. Of all cases, 94.21% were ductal, 2.63% were mucinous, and 2.11% were lobular. They were classified as grade I in 68.82% of the cases, grade II in 28.42% of the cases, and grade III in 3.16% of the cases. There was a significant association between histological grade and breast cancer subtypes (p < 0.0001), but no correlation was found with age (p = 0.467). Conclusion: In our BC patients, the luminal A was predominant, while HER2-overexpressed was the least found. A strong association was noted between histological grade and molecular subtypes. These results should allow for important clinical and policy implications for BC control in the DRC.
