Abstract
Long-term breastfeeding is a modifiable, protective factor against breast cancer, particularly triple-negative breast cancer (TNBC), a highly aggressive subtype with limited therapeutic options. Recent findings suggest that the protective effects of breastfeeding are mediated not only through hormonal regulation and epithelial differentiation but also via the modulation of the breast microbiota. This review examines epidemiological data on the association between breastfeeding duration and TNBC risk reduction, highlights the composition and functions of breast microbiota in health and disease, and discusses how dysbiosis may contribute to carcinogenesis. By examining the microbiome's role in maintaining breast health, we emphasize how breastfeeding contributes to a natural defense system against TNBC, offering a unique perspective on the intersection of maternal health, microbiology, and cancer prevention. Breastfeeding not only provides maternal and infant benefits but also emerges as a biological strategy that promotes cancer resistance through its influence on the breast microbiota. Integrating epidemiological, microbiological, and mechanistic evidence suggests that future research deliberately combining these domains will be essential to clarify causal pathways and translate findings into prevention and intervention strategies against TNBC.