What Causes Nipple Discharge?

Premenopausal and Postmenopausal Breast Discharge

Doctor talking to patient about the causes of nipple discharge
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Nipple discharge from the breasts, either before or after menopause can be very alarming. Discharge symptoms can vary widely from thin to thick and sticky, and may range in color from clear, to white and milky, to yellow-green, or even bloody. There are many potential causes including local irritation and hormonal changes; infections and abscesses; and though not common, can even be the first sign of breast cancer. It may also occur due to non-breast related conditions such as thyroid disease or with certain medications. Let's look at what you need to know if you develop nipple discharge at any time.

Types, Signs, and Symptoms

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

Timing

The most common causes of nipple discharge vary depending on whether a woman is premenopausal or postmenopausal, and if she is pregnant, breastfeeding, or has given birth in the past.

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 an underlying conditions such as a papilloma, ectasia, or even cancer, whereas bilateral discharge is more likely related to hormonal changes or systemic (system wide) conditions such as thyroid disease.

Spontaneous vs Discharge with Manipulation

Discharge may occur spontaneously, or may instead occur only with breast manipulation such as squeezing a nipple.

Single vs Multiple Ducts

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

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 such as blocked milk ducts or ectasia).

Color

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

  • Clear or "serous" with duct ectasia and cancer
  • Milky, such as in women who are breastfeeding, hormone-related causes, and with galactorrhea (see below) in women, men, or even infants
  • Yellow, often related to an infection
  • Green, commonly seen with fibrocystic disease
  • Brown, often with fibrocystic disease or mammary duct ectasia
  • Bloody: Bloody discharge may be a sign of breast cancer but is more likely to be due to another condition such as an intraductal papilloma

Associated Symptoms

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), a breast mass when combined with discharge is highly suggest of breast cancer, and missed periods may be a sign of pregnancy or hyperpolactinemia. Some of the conditions that cause discharge may also cause breast pain.

Causes

It's thought that 50 to 80 percent of women have at least a drop or two of discharge at some point in their lives, and there are many potential causes. Most often, these causes are benign, though roughly 7 percent to 15 percent of women who have discharge significant enough to visit their doctor are found to have breast cancer. Signs that are concerning for cancer include one-sided discharge that occurs spontaneously, discharge that is bloody, discharge that occurs from only one duct, and the presence of other symptoms of breast cancer, such as skin changes (dimpling or retraction), nipple inversion, a breast mass, and more. Possible causes of breast discharge include:

Pregnancy-Related

Nipple discharge can be normal during pregnancy, when colostrum begins to flow, and certainly after delivery. Colustrum 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 may have breast discharge before their periods. Symptoms may include breast pain, lumpy breasts, and a yellow-green or brown discharge.

Hormonal Changes and Medications

Normal hormonal changes, as well as medications such as birth control pills may cause nipple discharge.

Infections (Mastitis or Abscess)

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

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

Medications

Hormonal therapies such as birth control pills also sedatives, often cause a milky discharge

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, and is referred to as galactorrhea. It is most often due to an increased level of the hormone prolactin in the blood (a hormone secreted by the pituitary gland that is 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: Benign growths in the pituitary gland in the brain

Mammary Duct Ectasia (Dilated 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 is often accompanied by nipple tenderness and redness. It may lead to a secondary bacterial infection (mastitis) and can also cause the nipples to turn inwards (nipple inversion) raising concern about breast cancer. It usually goes away in time, with relief provided by hot packs, but sometimes requires surgical treatment.

Intraductal Papillomas

Intraductal papillomas are usually benign growths that most often involve 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 is often non-tender. Most are benign, but they may contain regions of papillary carcinoma of the breast, a type of ductal carcinoma in situ (DCIS). A ductogram or needle biopsy may be done, and if there is concern, the papilloma can be surgically removed.

Breast Cancer and Carcinoma in Situ

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 a woman over the age of 40, is associated with a breast mass, is bloody, unilateral, or involves only one duct.

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.

Around 7 percent to 15 percent of people who present to their doctor with nipple discharge have an underlying breast cancer that is responsible.

Paget's Disease of the Breast

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 is 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.

Nipple Discharge After Menopause and in Men

Most nipple discharge occurs in women who are premenopausal, especially women in the most fertile years.

Menopausal Nipple Discharge

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.

Nipple Discharge in Men

When men develop nipple discharge, there is often an underlying problem. An investigation looking for conditions such as an elevated prolactin level is important, but it's also very important to note that men can get breast cancer too, 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 men. As with women, nipple discharge was often an early warning sign of a pre-invasive cancer, of particular note as breast cancer in men is often diagnosed in later stages of the disease than women.

Nipple Discharge in Infants

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

Diagnosis

The approach to diagnosis your doctor takes 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 (cytology) to observe the cells present. While this test may show cancer cells, a negative cytology exam can't rule out cancer.

Ultrasound

An ultrasound examination 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.

Ductogram/Galactogram

A ductogram is a test that involves injecting a dye to evaluate the milk ducts. This test, as well as tests such as ductal lavage and ductoscopy are not available everywhere.

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) may be done as well.

If a prolactin level is elevated with no apparent cause, a brain MRI or CT may be done to look for the presence of a pituitary microadenoma.

Biopsy

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

Tests to Diagnose Breast Cancer

If breast cancer is a possibility, tests to diagnose the disease may include

  • Mammogram
  • Breast ultrasound
  • Breast MRI
  • Breast biopsy

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 needed. 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 warm packs until the condition resolves on its own.

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.

Sources:

Lobo RA, Gershenson DM, Lentz GM, Valea FA, eds. Comprehensive Gynecology. 7th ed. Philadelphia, PA: Elsevier; 2017

Morrogh, M., and T. King. The Significance of Discharge of the Male Breast. The Breast Journal. 2009. 15(6):632-638.

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