The tumor microenvironment is a well-recognized contributor to cancer progression in solid tumors. Cancer cell interactions with abnormal extracellular matrix, tumor associated immune and stromal cells, and aberrant fluid flow all contribute to cancer progression. Breast tumors are often characterized by a dense collagenous stroma and a hypoxic core. A recently identified and little understood component of the breast tumor microenvironment is the breast microbiome. The work described here elaborates on the importance of the tumor microenvironment in cancer progression and demonstrates the importance of studying cancer-microbiome interactions in the context of tumor microenvironmental stimuli.