title: The Microbiome of Aseptically Collected Human Breast Tissue in Benign and Malignant       Disease
design: Globally breast cancer is the leading cause of cancer death among women.         The breast consists of epithelium, stroma and a mucosal immune system that make up a complex         microenvironment. Growing awareness of the role of microbes in the microenvironment recently         has led to a series of findings important for human health. The microbiome has been         implicated in cancer development and progression at a variety of body sites including         stomach, colon, liver, lung, and skin. In this study, we assessed breast tissue microbial         signatures in intraoperatively obtained samples using 16S rDNA hypervariable tag sequencing.         Our results indicate a distinct breast tissue microbiome that is different from the         microbiota of breast skin tissue, breast skin swabs, and buccal swabs. Furthermore, we         identify distinct microbial communities in breast tissues from women with cancer as compared         to women with benign breast disease. Malignancy correlated with enrichment in taxa of lower         abundance including the genera Fusobacterium, Atopobium, Gluconacetobacter, Hydrogenophaga         and Lactobacillus. This work confirms the existence of a distinct breast microbiome and         differences between the breast tissue microbiome in benign and malignant disease. These data         provide a foundation for future investigation on the role of the breast microbiome in breast         carcinogenesis and breast cancer prevention. 