Fluid that leaks from one or both nipples is called a nipple discharge. Each breast has several (15 to 20) milk ducts. A discharge can come from one or more of these ducts.
Nipple discharge can occur normally during the last weeks of pregnancy and after childbirth when breast milk is produced. A nipple discharge can also be normal in women who are not pregnant or breastfeeding, especially during the reproductive years. For example, in women, fondling, suckling, irritation from clothing, or sexual arousal can stimulate a nipple discharge, as can stress. However, a nipple discharge in men is always abnormal.
A normal nipple discharge is usually a thin, cloudy, whitish, or almost clear fluid that is not sticky. However, the discharge may be other colors, such as gray, green, yellow, or brown. During pregnancy or breastfeeding, a normal discharge is sometimes slightly bloody. Abnormal discharges vary in appearance depending on the cause. An abnormal discharge may be accompanied by other abnormalities, such as dimpled skin, swelling, redness, crusting, sores, and a retracted nipple. (A nipple is retracted if it pulls inward and does not return to its normal position when it is stimulated.) If a discharge from only one breast occurs on its own (without any stimulation of the nipple), it may be abnormal.
Several disorders can cause an abnormal discharge. A discharge from one milk duct or from one breast is likely to be caused by a problem with that breast, such as a noncancerous (benign) or cancerous breast tumor. A discharge from both breasts or from several milk ducts in one breast is more likely to be caused by a problem outside the breast, such as a hormonal disorder or use of certain drugs.
Usually, the cause is a benign disorder of the milk ducts:
Intraductal papilloma is the most common cause. It is also the most common cause of a bloody nipple discharge when there is no lump in the breast.
Less common causes:
Certain disorders stimulate the production of breast milk in women who are not pregnant or breastfeeding. In most of these disorders, the level of prolactin (a hormone that stimulates production of breast milk) is elevated. Taking certain drugs can have the same effect.
Cancer causes fewer than 10% of cases.
Nipple discharge is a cause for concern when it
When to see a doctor:
If a nipple discharge continues for more than one menstrual cycle or if any of the warning signs are present, women should see a doctor. Delay of a week or so is not harmful unless there are signs of infection such as redness, swelling, and/or a discharge of pus. Women with such symptoms should see a doctor within 1 or 2 days.
What the doctor does:
Doctors first ask questions about the woman's symptoms and medical history. Doctors then do a physical examination. What they find during the history and physical examination often suggests a cause of the discharge and the tests that may need to be done (see Table below).
To help identify the cause, doctors ask about the discharge and about other symptoms that may suggest possible causes. Women are also asked whether they have had disorders or take drugs that can increase prolactin levels.
Doctors examine the breast, looking for abnormalities, including lumps (see Warning signs). If the discharge does not occur spontaneously, the area around the nipples is gently pressed to try to stimulate a discharge.
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If doctors suspect that a hormonal disorder is the cause, blood tests are done to measure the levels of prolactin and thyroid-stimulating hormone.
If a pituitary or brain disorder is suspected, magnetic resonance imaging (MRI) or computed tomography (CT) of the head is done.
If the discharge is not obviously bloody, it is analyzed to determine whether it contains small amounts of blood. If blood is present, a sample of the discharge is examined under a microscope (called cytology) to look for cancer cells.
If a lump can be felt, ultrasonography is done. Testing is similar to that for any breast lump (see Testing). Cysts are drained (by aspiration), and the fluid is tested. If cysts remain after aspiration or if lumps are solid, mammography is done, followed by a biopsy.
When there is no lump but cancer is still suspected or when other test results are unclear, mammography is done.
If ultrasonography and mammography do not identify a cause and the discharge occurs spontaneously and comes from one milk duct, doctors usually do an imaging test (such as MRI) after a contrast agent (which helps make images clearer) is injected into the duct. This test can help rule out or identify cancer.
If no lump can be felt and the mammogram is normal, cancer is highly unlikely. Sometimes a specific cause cannot be identified.
If a disorder is identified, it is treated. If a noncancerous tumor or disorder is causing a discharge from one breast, the duct that the discharge is coming from may be removed. This procedure requires only a local anesthetic and does not require an overnight stay in the hospital.
Last full review/revision March 2014 by Mary Ann Kosir, MD