Breast Mammogram and Tissue Study

Background: Women whose mammograms show a lot of dense areas are more likely to develop breast cancer and to have cancers that are missed by mammograms. It is unclear why some factors lead to having dense breasts and why having dense breasts increases the risk of developing breast cancer. Objectives: To determine why some women s breasts look dense on mammograms. To determine what types of cells and tissues make up dense areas of breasts and why these tissues may be more likely to become cancerous. Eligibility: Women between 40 and 65 years of age who have not had breast cancer or received medicines or radiation for any type of cancer and who are scheduled to undergo a breast biopsy. Design: This study is conducted at the University of Vermont, in collaboration with the NCI. Participants undergo the following: * Review of their medical records collected over the last 2 years by the Vermont Mammography Registry. * Participation in a short telephone interview. * Height and weight measurement. * Testing of biopsy tissue collected for diagnosis or treatment. * Future contacts regarding health status for up to 10 years, including review of additional mammograms, removed tissues, questionnaires and medical records collected by the Vermont Mammography Registry during the 10-year study. Participants may also undergo the following optional procedures: * Provide a mouthwash sample for genetic testing. * Provide a blood sample to test for markers of dense mammograms or breast cancer.