Breast Density

Radiologists grade breasts on the basis of how dense they are. Dense breasts have a high proportion of ductal and connective tissue, while less-dense breasts have a higher proportion of fatty tissue. The four commonly used categories are: (1) entirely fat, (2) scattered fibroglandular densities, (3) heterogeneously dense, and (4) extremely dense. Women with dense breasts have a higher risk of developing breast cancer.

How Breast Anatomy Changes

Everyone, male and female, is born with a small amount of breast tissue, but only the presence of certain hormones, particularly estrogen and progesterone, can stimulate the development of that tissue into breasts. In girls, the small patch of breast tissue in each breast lies dormant until puberty. At puberty, hormones stimulate the breast tissue to grow and form the mature system of lobules and ducts. Breast tissue remains inactive until pregnancy, when the lobules begin to multiply and produce milk.

In menopause, hormone production slows. The number of lobules in the breast decreases and the ones that remain shrink in size. Breast density diminishes, and a larger proportion of the breast is made up of fat than in younger women.