Causes

The exact cause of fibrocystic breast changes isn't known, but experts suspect that reproductive hormones — especially estrogen — play a role.

Fluctuating hormone levels during the menstrual cycle can cause breast discomfort and areas of lumpy breast tissue that feel tender, sore and swollen. Fibrocystic breast changes tend to be more bothersome before your menstrual period and ease up after your period begins.

When examined under a microscope, fibrocystic breast tissue includes distinct components such as:

• Fluid-filled round or oval sacs (cysts)
• A prominence of scar-like fibrous tissue (fibrosis)
• Overgrowth of cells (hyperplasia) lining the milk ducts or milk-producing tissues (lobules) of the breast
• Enlarged breast lobules (adenosis)