Breast cysts are fluid-filled lumps within the breast and most are caused by different hormonal changes throughout a woman’s body such as during menstruation. Breast cysts are often described as round lumps with distinct edges and are usually benign (non cancerous). They do not require treatment unless the cyst is large and painful, in which case, draining fluid from the cyst can ease symptoms.


Symptoms of breast cysts may include:

  • Formation of a lump or swelling of thickened breast tissue usually found in one breast; however, can occur in both breasts at the same time
  • Persistent pain in the breast
  • Breast sensitivity
  • Growth in breast lump just before menstruation
  • Decrease in breast lump after menstruation


The cause of breast cysts remains unknown. Breast cysts develop when there is an excess growth of glands and connective tissue blocking milk ducts (used for production of milk during pregnancy and breast feeding), in turn causing them to expand and fill up with fluid.

  • Microcysts: Small cysts that are difficult to feel but may be seen during imaging tests (ultrasound).
  • Macrocysts: Large cysts (1-2 inches) that can put pressure on the breast and cause breast pain and soreness.