Each of your breasts contains lobes of glandular tissue, arranged like petals of a daisy. The lobes are divided into smaller lobules that produce milk during pregnancy and breast-feeding. The supporting tissue that gives the breast its shape is made up of fatty tissue and fibrous connective tissue.  Breast cysts develop as a result of fluid accumulation inside the glands in the breasts.

Breast cysts may be defined by their size:

  • Microcysts are too small to feel, but may be seen during imaging tests, such as mammography or ultrasound.
  • Macrocysts are large enough to be felt and can grow to about 1 to 2 inches (2.5 to 5 centimeters) in diameter. Large breast cysts can put pressure on nearby breast tissue, causing breast pain or discomfort.

Experts don't know what causes breast cysts. They may develop as a result of hormonal changes from monthly menstruation. Some evidence suggests that excess estrogen in your body, which can stimulate the breast tissue, may contribute to breast cysts.

Oct. 08, 2015