Signs and symptoms of fibrocystic breasts may include:

• Breast lumps or areas of thickening that tend to blend into the surrounding breast tissue
• Generalized breast pain or tenderness
• Breast lumps that fluctuate in size with the menstrual cycle
• Green or dark brown nonbloody nipple discharge that tends to leak without pressure or squeezing
• Breast changes that are similar in both breasts
• Monthly increase in breast pain or lumpiness from midcycle (ovulation) to just before your period

Fibrocystic breast changes occur most often in women in their 20s to 50s. Rarely do postmenopausal women experience fibrocystic breast changes, unless they're on hormone therapy.

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 your 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 the pain and lumpiness tends to clear up or lessen once your menstrual 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)

Having fibrocystic breasts doesn't increase your risk of breast cancer.