When we look at a mammogram, one of the first things we look at is breast density – the amount of fibroglandular tissue in the breast compared to the amount of fat. The higher proportion of breast tissue to fat, the denser the breast. Why does breast density matter? On a mammogram, fat looks dark grey or black whereas breast tissue looks white. That white area can be an issue because many small breast cancers also appear as white, so it’s harder to detect them in dense breasts. In this important segment, Marie Quinn, MD, Assistant Professor of Oncology in the Department of Diagnostic Radiology at Roswell Park Cancer Institute, discusses why women should know if they have dense breasts and how breast density can affect cancer risk.