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Neoplastic diseases are characterized by changes to multiple microbiome compartments that is termed dysbiosis. Among the compartments, the dysbiosis of the gut microbiome plays pivotal role due to the large quantity of the bacteria in the compartment and the consequential large biosynthetic capacity. The connections between the microbiome, the host and the tumor a multidirectional, in other words, the tumor supports or induces the dysbiosis of the gut microbiome, while the microbiome supports cancer progression. We will review the possible anterograde and retrograde connections between the microbiome and breast carcinoma. These discussions will include the identification and characterization of hormone-like bacterial metabolites with anti- and proneoplastic properties. Bioactive bacterial metabolites acting on cancer cells evoke mild induction of oxidative stress primarily through reducing NRF2 activity that induce multi-pronged pathways resulting in inhibiting key cancer hallmarks as the epithelial-to-mesenchymal transition, cell movement or cancer stem cell formation. Alongside, compositional changes to the microbiome, and finally, a novel catecholamine-dependent pathway contributing to gut dysbiosis will be discussed. Possible intervention points will be discussed and identified.