Cysts are fluid filled sacs within the breast. These sacs form when normal milk-producing glands enlarge. The cause of this enlargement is not definitely known but is very likely related to an imbalance between the normal production and absorption of fluid. Breast cysts may be solitary but are most commonly multiple and can vary in size from microscopic to larger than a ping-pong ball.

Breast cysts are common, particularly in women age 40-60. Although larger cysts can sometimes be felt as “lumps”, many cysts are undetectable by physical examination.

Cysts are frequently seen as round masses on mammograms. When this occurs, breast ultrasound examination is usually performed. Breast ultrasound is the most sensitive and accurate method for the identification and diagnosis of breast cysts. With modern ultrasound equipment, accuracy rate of 95% to 100% can be expected.

Virtually all breast cysts identified as “simple cysts” by ultrasound are benign and remain so. It is estimated that perhaps 1 in 1,000 cysts may harbor a tumor (not necessarily malignant). These can usually be identified by their ultrasound appearance. Women with cysts are not at greater risk for the development of cancer although this risk may be minimally elevated if there is a positive family history for breast cancer (mother, sister, daughter).

Cyst aspiration is a a simple and effective technique which serves a dual purpose. It confirms the nature of the lump as “cystic” or “solid” and extracts fluid from a cyst which frequently makes the lump disappear. If no fluid is obtained, the lump is presumed not to be a cyst and whatever material is aspirated may be sent to the laboratory for analysis. When a cyst is discovered by ultrasound, aspiration is not generally recommended unless the cyst has some unusual features on the ultrasound image, or the cyst is associated with discomfort (physical or emotional) which can be relieved by aspiration.

If the cyst appears to contain material other than fluid on the ultrasound image, an aspiration procedure may be recommended. This is best performed using ultrasound guidance to ensure complete drainage of the cyst.