Nipple discharge occurs when fluid leaks out of your nipple. Sometimes it just happens, and sometimes it happens only when you squeeze your nipple. It can happen in both of your nipples or only one. The color and consistency of the discharge depends on what’s causing it. Nipple discharge in a man should always be evaluated by a doctor.

When he is born, a man’s breasts contain the same tissue and milk ducts as a woman’s, but because they are exposed to male hormones instead of female hormones during puberty, they become mostly fat instead of growing bigger. Some of the tissue and milk ducts are left though, so many of the causes of nipple discharge are the same in men and women.

Nipple discharge doesn’t happen very often in men. When it does happen, it’s very important that you see your doctor because it may be a sign that you have breast cancer.

Nipple discharge is almost always a sign that something else is going on that is causing it. There are only a handful of things that cause your nipple to produce a discharge if you are a man. These causes include:

Puberty

Men who are going through puberty may experience nipple discharge because of the changing hormone levels in their body. Squeezing and manipulating the nipples can cause discharge to happen more frequently.

Breast cancer

Accompanying symptoms may include:

  • bloody or clear discharge
  • discharge from only one nipple
  • often, discharge is accompanied by a small, firm lump in the breast
  • sometimes your nipple will change from sticking out to sticking in, which is called an inverted nipple
  • you may feel swollen lymph nodes, which feel like hard lumps, in your armpit

Learn more about breast cancer.

Duct ectasia

This occurs when the milk ducts beneath your nipple get blocked and become inflamed. Accompanying symptoms may include:

  • only one breast being affected
  • discharge that is greenish or multicolored, thick, and sticky
  • swollen, painful, and itchy nipple
  • a lump that develops from scar tissue or infection, as well as bloody discharge
  • duct ectasia that’s benign, not cancerous, and doesn’t increase your risk of getting cancer

Learn more about duct ectasia.

Gynecomastia

This is a condition in which one or both of a man’s breasts become large and swollen.

Accompanying symptoms may include a tenderness and burning sensation in your breasts.

Learn more about gynecomastia.

Breast infection

Breast infections are most common in women who are breastfeeding, but men can develop them too. Accompanying symptoms may include:

  • thick discharge that has a green tinge
  • one affected breast
  • breasts that feel warm and sore and look red

Learn more about breast infections.

Intraductal papilloma

This is a noncancerous growth in the milk ducts of the breast. Accompanying symptoms may include:

  • breast enlargement
  • either a large lump near the nipple or multiple small lumps farther away from the nipple
  • bloody and sticky discharge

Learn more about intraductal papilloma.

Pituitary tumor

Your pituitary gland controls the hormone that causes a woman’s breasts to produce milk. A prolactinoma is a tumor that can grow in the pituitary gland and produces a hormone called prolactin. Prolactin reduces testosterone in men and estrogen in women. Accompanying symptoms may include:

  • larger breasts
  • milky discharge
  • impotence (inability to have an erection or ejaculate)

Learn more about pituitary tumors.

Treatment of your nipple discharge depends on what is causing it and includes:

  • antibiotics for infections
  • surgery to remove tumors and severely blocked ducts
  • treatment of the underlying cause
  • medication, such as radiation therapy or chemotherapy

All men who have nipple discharge should see their doctor because it can be a sign of an infection or a serious illness like breast cancer.

Infections and breast cancer have better outlooks if they’re diagnosed and treated in the earliest stages.