An Overview of Nipple Discharge

Nipple discharge is very common and rarely dangerous

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Nipple discharge or fluid from the breasts can be very alarming, but it's normal in many women. So normal that when renowned breast surgeon Susan Love, M.D., conducted a study where gentle suction was applied to women's breasts, 83 percent of the women—old, young, mothers, non-mothers, previously pregnant, never pregnant—had some amount of discharge.

There are many different presentations of nipple discharge, as well as many potential causes. While precancers and cancers can be to blame, they rarely actually are. Nevertheless, if you are worried, see your doctor. Color and consistency, among other things, can help determine what might cause for concern.

nipple discharge color
Verywell / Jessica Olah

Symptoms

Nipple discharge can vary in a number of different ways, and some of these can give clues to the possible underlying causes.

Timing and Circumstance

Nipple discharge, at least cases related to the most common causes, may appear a specific periods in a woman's life. This can vary depending on whether a woman is premenopausal or postmenopausal, and if she is pregnant, breastfeeding, or has given birth in the past.

Discharge may occur spontaneously (suddenly and without external influence) or only with breast manipulation, such as squeezing the nipple.

Consistency

Nipple discharge may be thin and clear, slightly thicker and milky, purulent (pus-like) and cloudy (with infections), or very thick, sticky, and cheese-like (with conditions like blocked milk ducts, a.k.a. ectasia).

Color

The color of breast discharge is also very important when it comes to determining underlying causes. Colors may include:

Nipple Discharge Color Possible Cause(s)*
Clear (serous) Blocked milk ducts, breast cancer
Milky white Breastfeeding, hormone changes, galactorrhea
Yellow Infection
Green Blocked milk ducts, 
fibrocystic breast disease
Brown Fibrocystic breast disease
Red (bloody) Intraductal papilloma, breast cancer

*These are possible reasons, though there are others. Only your doctor can determine what's responsible for your nipple discharge.

Unilateral vs. Bilateral

Nipple discharge may occur on one side (unilateral) or on both sides (bilateral). Unilateral discharge is more likely to be related to underlying conditions such as intraductal papilloma, ectasia, or even cancer. Bilateral discharge, on the other hand, is more likely related to hormonal changes or systemic (system-wide) conditions, such as thyroid disease.

Single vs. Multiple Ducts

Discharge may occur from a single breast duct or from multiple ducts. Again, discharge from a single duct is more likely to be due to a local condition affecting the breast.

Other

Nipple discharge may occur alone, but if associated symptoms are present, they may give clues as to the cause. For example:

  • A fever may suggest a breast infection (mastitis).
  • Missed periods may be a sign of pregnancy or hyperprolactinemia (high levels of the hormone prolactin).
  • A breast mass when combined with discharge is highly suggestive of breast cancer.

Some of the conditions that cause discharge may also cause breast pain.

Causes

The ducts of the female nipple are pipelines made to carry milk, so a little fluid shouldn't be surprising, says Dr. Love. There are many potential causes of breast discharge, including the following.

Pregnancy-Related

Nipple discharge can be normal during pregnancy, when colostrum begins to flow, and certainly after delivery. Colostrum, the first secretion from the mammary glands after giving birth, usually appears thin and light-yellow in color and turns thicker and milky white later on.

Local Irritation/Inflammation

Irritation of the nipples from rough clothing or an improperly fitting bra, as well as excess stimulation or trauma to the breasts, may cause discharge.

Fibrocystic Changes

Premenopausal women who have fibrocystic breasts—where healthy breast tissue feels lumpy and may be painful at times—may have breast discharge before their periods. It may be yellow-green or brown.

Hormonal Changes

Normal hormonal changes, such as those that occur with menstruation, may cause nipple discharge.

In particular, conditions related to prolactin level changes—in men or women—may be to blame.

Medications

Hormonal therapies (e.g., birth control pills) and sedatives often cause a milky discharge.

Infections

Mastitis is a breast infection that may cause purulent (pus-like) yellow-green discharge along with a fever, pain, and breast tenderness.

A breast abscess is a localized area in which the body has "walled off" an infection. Nipple or subareolar abscesses may especially lead to discharge, which is similar to that with mastitis, but is often foul-smelling as well.

Blocked Milk Ducts

Mammary duct ectasia, or blocked milk ducts, is a condition most often found in women who are nearing menopause (perimenopause) or after menopause. It occurs when the breast ducts widen and become clogged with thick discharge.

The discharge can be green, brown, or even black, and very thick and cheese-like. It's often accompanied by nipple tenderness and redness.

The condition may lead to a secondary bacterial infection (mastitis) and can also cause the nipples to turn inward (nipple inversion), raising a concern about breast cancer. Mammary duct ectasia usually goes away in time, with relief provided by hot packs, but it sometimes requires surgical treatment.

During perimenopause and menopause, the most common causes of nipple discharge change significantly. Conditions such as mammary duct ectasia and cancer are more common, and should not be dismissed until a thorough workup has been done.

Galactorrhea/Hyperprolactinemia

A milky discharge, similar to that seen in women who are breastfeeding, may occur in women who aren't breastfeeding, men, or even young children. This is referred to as galactorrhea.

It's most often due to an increased blood level of prolactin, a hormone secreted by the pituitary gland that's involved with breast development and breastfeeding, in a condition referred to as hyperprolactinemia. In women, hyperprolactinemia is often accompanied by amenorrhea (lack of menstrual periods), but in men, nipple discharge may be the first symptoms.

There are a number of potential causes of elevated prolactin levels, including:

  • Medications: Drugs known to elevate prolactin levels include some high blood pressure medications, opioids, some antidepressants, antipsychotics, and some drugs used for acid reflux.
  • Herbal supplements, such as fenugreek, red clover, anise, and fennel
  • Hypothyroidism
  • Pituitary microadenomas, or benign growths in the pituitary gland in the brain

Intraductal Papillomas

Intraductal papillomas are usually benign growths that, by and large, involve only a single duct. They are most common in premenopausal women and often cause a clear or bloody discharge. A lump may be felt on the nipple, but it's often not tender.

Though most are not a concern, they may contain regions of papillary carcinoma of the breast, a type of ductal carcinoma in situ (DCIS, a precancerous condition).

Breast Cancer and Carcinoma in Situ

For 7 percent to 15 percent of people who have nipple discharge, an underlying breast cancer is responsible. While breast cancer is not a common cause of nipple discharge, it can be an early warning sign of breast cancer that is still in the preinvasive stage (ductal carcinoma in situ), especially when it occurs in someone over the age of 40 and/or the following apply:

  • Discharge is one-sided discharge and occurs spontaneously
  • Discharge is bloody
  • Discharge occurs from only one duct of the tree-branch-like network of ducts that converge at the nipple
  • Other symptoms of breast cancer, such as skin changes (dimpling or retraction), nipple inversion, a breast mass, etc., are present

Though nipple discharge related to breast cancer is often thought to be bloody, this is not necessarily the case, and the discharge may be clear or milky. This reinforces the fact that any nipple discharge that does not have an obvious cause (and even if it does at times) should be evaluated.

Male Breast Cancer

It's very important to note that women and men can get breast cancer, and male breast cancer is often under-recognized, even among physicians. Little research has looked at discharge in men, but one older study from 2009 found that nipple discharge was associated with breast cancer in 57 percent of male cases.

As with women, nipple discharge was often an early warning sign of a pre-invasive cancer. This is of particular note as breast cancer in men is often diagnosed in later stages of the disease than women, when it's harder to treat.

Paget's Disease

Paget's disease of the breast is an uncommon form of breast cancer, accounting for only 1 percent to 4 percent of cases. In addition to nipple discharge that's often bloody, it may cause nipple tenderness or burning, and redness, scaling, or flaking of the nipple. A biopsy is usually needed to make the diagnosis.

In Infants

Small amounts of clear to milky nipple discharge (and often some breast swelling or a small lump) in newborns is fairly common, and it's related to hormones left over from pregnancy. Later in infancy, bloody discharge may occur, usually due to mammary duct ectasia.

Diagnosis

What your doctor does to reach a diagnosis will depend on your age and any other symptoms of findings on physical exam. Possible tests may include:

Cytology

A sample of the discharge may be evaluated under the microscope in the lab to observe the cells present. While this may show cancer cells, a negative cytology exam can't rule out cancer.

Blood Tests

A serum prolactin level is often drawn if a milky discharge occurs in someone who is not pregnant or hasn't been pregnant. A thyroid test (TSH) test may be done as well.

Imaging

An ultrasound examination, which uses sound waves, is a common test to look for abnormalities in the area behind nipple and areola. It can be used to identify conditions such as papillomas, though a biopsy is often still necessary (see below).

A ductogram is a test that involves injecting a dye to evaluate the milk ducts. While helpful is some cases, this—as well as screening tools like ductal lavage and ductoscopy—are not available everywhere.

If a prolactin level is elevated with no apparent cause, a brain magnetic resonance imaging (MRI) scan or computed tomography (CT) scan may be done to look for the presence of a pituitary microadenoma, a benign tumor of the pituitary gland.

Biopsy

A breast biopsy may be done to evaluate a lump near the nipple, including a skin biopsy if Paget's disease is suspected.

If breast cancer is a possibility, a breast MRI, ultrasound, biopsy, and a mammogram may all be considered.

Treatment

The treatment options for nipple discharge will depend on the underlying cause. With some causes, such as discharge in later pregnancy, reassurance is all that's needed.

Infections are usually treated with antibiotics, though if an abscess is present, drainage is often required.

For fibrocystic disease, aspiration of a breast cyst or cysts may resolve the problem.

Intraductal papillomas are often surgically removed if they are symptomatic.

Mammary duct ectasia doesn't usually require treatment, other than the application of warm packs until the condition resolves on its own.

Treatment options for breast cancer include surgery, as well as chemotherapy and radiation.

A Word From Verywell

As noted above, there are many potential causes of breast discharge. While breast cancer is not a common cause, nipple discharge as a sign of breast cancer often occurs when the tumor is still very small and non-invasive. When tumors are removed at this stage, they should be, at least in theory, 100 percent curable.

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