The intratumoral microbiota in breast cancer: from basic research to clinical translation

Breast cancer remains a leading global malignancy among women, with increasing incidence and mortality. Recent advances in multi-omics technologies have revealed the presence of diverse microbial communities in the tumor microenvironment, comprising bacteria, viruses, and fungi. These microbes play complex roles within tumor initiation and progression, affecting local inflammation and modulating host metabolism, genomic stability, and immune responses. Emerging evidence indicates that the intratumoral microbiota holds diagnostic potential and represents a novel biomarker for molecular subtyping and prognosis. Furthermore, intratumoral microbiota offer new avenues for targeted interventions, such as engineered bacteria and phage therapy, which may overcome limitations of conventional treatments. This review summarizes current insights into the composition, colonization pathways, mechanisms, and clinical applications of intratumoral microbiota, underscoring their potential to advance precision medicine in breast cancer.