Inflammation has been confirmed to exist in the tumor microenvironment, while the risk of cancer occurrence increases in cases of chronic inflammation. It is estimated that approximately 10% to 20% of cancers are associated with chronic infections and attendant inflammation. Bacteria, both pathogenic and commensal, viruses, and fungi actively participate in the development and maintenance of inflammation and tumor growth in humans. The exposome, which is a sum of human environmental exposures, such as industrial diet, consumed drugs, and toxins, affects the composition and function of the human microbiome, which could lead to dysbiosis and disorders in tissue homeostasis through different mechanisms, including the intensification of the immune response, activation and abnormal proliferation, and disruption to epithelial barrier integrity. Presently, science remains at the stage of revealing the complexity associated with the mechanisms involved in building relationships that cover the microbiome–inflammation–tumor, yet it is already known how important it is to care for microbial homeostasis of the organism.