A breast cyst is a cyst, a fluid-filled sac, within the breast. One breast can have one or more cysts. They are often described as round or oval lumps with distinct edges. In texture, a breast cyst usually feels like a soft grape or a water-filled balloon, but sometimes a breast cyst feels firm.

Breast cysts can be painful and may be worrisome but are generally benign. They are most common in pre-menopausal women in their 30s or 40s. They usually disappear after menopause, but may persist or reappear when using hormone therapy. They are also common in adolescents. Breast cysts can be part of fibrocystic disease. The pain and swelling is usually worse in the second half of the menstrual cycle or during pregnancy.

Treating breast cysts is usually not necessary unless they are painful or cause discomfort. In most cases, the discomfort they cause may be alleviated by draining the fluid from the cyst. The cysts form as a result of the growth of the milk glands. While some large cysts feel like lumps, most cysts cannot be identified during physical examinations.

Breast cysts are not to be confused with "milk cysts" (galactoceles), which usually appear during weaning.

Signs and symptoms of breast cysts include:

Lumps in the breast are often not found during self-examinations or physical exams. However, in some cases they can be felt at touch, especially if they are larger.

Breasts are usually lumpy or nodular as a result of the hormonal changes that women go through during their menstrual cycle. However, new breast lumps should always be referred to a specialist.

Cysts can also be confused with infections that form on the nipple or the areola. A common cyst look-alike is a localised infection of a duct in the nipple. These can happen whether you're breast feeding or not, (if you are breast feeding it could also be a bleb) this becomes a bump that may then start to look yellow and white (pus filled). Check with your doctor if you are unsure or have other symptoms that are worrying you.