High breast density and aging are the strongest risk factors for sporadic breast cancer among women. Although glandular epithelium contributes to mammographic density, non-epithelial tissue components represent its major determinants: adipose tissue is radiolucent and fibrous tissue is dense. The hypothesis is that epidemiologic factors associated with elevated breast density alter the breast microenvironment (ME) (defined as all cells and structures surrounding luminal glandular cells including: myoepithelial cells; basement membrane, stromal fibroblast and myofibroblasts; endothelial cells and pericytes; inflammatory cells, collagens, matrix proteins, growth factors, hormones, and other biochemical components) in a manner that enhances dysregulated proliferation of breast epithelium and ultimately cancer. Specifically, the Investigators propose that epidemiologic factors that lead to increased exposure to hormones and inflammatory mediators alter the ME, leading to both increased breast density and cancer. The critical importance of the ME in carcinogenesis is supported by experimental and clinical data showing that epithelial abnormalities alone are generally insufficient for cancer development without concurrent changes in the ME.

The primary aim of this pilot study is to demonstrate the feasibility of collecting the data needed to elucidate the biologic mechanisms that mediate the substantial breast cancer risk associated with high mammographic density. Specifically, the Investigators will develop, fine tune, and validate a complex cross-sectional study protocol to collect risk factor data and biological specimens (blood, buccal cells, tissue fluids, and tissue) required to discover mechanisms and biomarkers that link high mammographic density (as measured quantitatively using computerized methods) to breast cancer risk. They will enroll 250 women between the ages of 40 to 65 years undergoing a radiologically guided biopsy at the University of Vermont, the largest center within the Vermont Breast Cancer Surveillance System (VBCSS), to participate in this pilot study of mammographic density.