Narrative review examines microorganisms in breast cancer with limited evidence from cross-sectional studies and models

Photo by National Cancer Institute / Unsplash

Frontiers in Medicine Published May 28, 2026 Medically reviewed May 28, 2026 DOI ↗ By Dr. Amelia Tan, PhD · Internal Medicine & Chronic Disease

Key Takeaway

Note that evidence on microorganisms in breast cancer relies on cross-sectional studies and models.

This narrative review explores the association between microorganisms and breast cancer. The scope of the article focuses on existing literature rather than new clinical trial data. No specific population, sample size, or intervention details were provided in the source text. The review synthesizes qualitative arguments regarding microbial involvement in the disease process.

The authors highlight significant limitations in the current evidence base. The majority of evidence originates from cross-sectional studies and in vitro or in vivo models. These study designs prevent definitive causal conclusions about the relationship between microorganisms and cancer development. No adverse events or safety data were reported in the source material.

Practice relevance is not explicitly defined by the authors. Clinicians should interpret findings with caution due to the reliance on observational and experimental models. The review does not provide specific dosing, efficacy rates, or comparative outcomes. Further high-quality research is needed to clarify the clinical implications of these observations.

Study Details

Study typeSystematic review

EvidenceLevel 1

PublishedMay 2026

View Original Abstract ↓

Breast cancer is a complex pathological process involving multiple factors and stages, characterized by pronounced molecular and phenotypic heterogeneity. Its global incidence and mortality rates have shown a continuous upward trend. With the advancement of microbiome research, microbial communities have been recognized as key determinants influencing host health and disease states. Increasing evidence suggests a close association between breast tissue–resident and systemic microbiota and the initiation and progression of breast cancer. Specifically, microorganisms may be associated with abnormal proliferation and malignant transformation of mammary epithelial cells through diverse mechanisms, including the modulation of estrogen metabolism, production of bioactive metabolites, induction of chronic inflammation, and remodeling of the tumor microenvironment. In addition, certain microbes may directly interact with host cells, potentially inducing DNA damage and contributing to the transition from normal to malignant phenotypes. This review systematically summarizes the origins and compositional characteristics of the breast microbiota, with a particular focus on current evidence regarding its roles in breast cancer initiation, progression, metastasis, therapeutic response, and prognosis. Currently, the majority of evidence originates from cross-sectional studies and in vitro/in vivo model, to better evaluate the current evidence, the limitations of different research designs and the levels of evidence are summarized in Table 1, aiming to provide new theoretical insights and research perspectives for microbiota-based strategies in breast cancer diagnosis and therapy.