What Is Mammary Duct Ectasia?

Medically Reviewed by Stephanie S. Gardner, MD on July 20, 2023
Written by WebMD Editorial Contributors
3 min read

Mammary duct ectasia may also simply be called duct ectasia. It is a benign breast condition caused by a milk duct widening and the surrounding skin thickening. This can lead to your milk duct becoming blocked, leading to fluid build-up. It can appear like a whitehead on your nipple.

Mammary duct ectasia happens when a single milk duct or several milk ducts under your nipple grow wider. As the surrounding skin thickens, your duct may fill with a thick, pus-like fluid. The substance may lead to blocking or clogging that is tender, painful, and swollen. You may have a whitehead on your nipple or unexplained nipple discharge.‌

Mammary duct ectasia is most common in the perimenopause period – between ages 45 and 55 years. It can also happen after menopause. ‌

If you feel a mass on your breast, talk to your doctor about getting an exam to rule out breast cancer. Rest assured that mammary duct ectasia doesn’t increase your risk for breast cancer or lead to breast cancer.

Your breasts are designed to create, store, and transfer milk when you have a baby. Inside your breast is a network of milk ducts and connective tissue. Medical professionals don’t know exactly what leads to a milk duct widening, but there are a few suspected causes.‌

Aging. As your body goes through hormone changes during perimenopause, your breast tissue changes. Over time the tissues transition from being mostly glandular tissue to mostly fatty tissue. During these changes, a duct may get clogged. ‌

Smoking. If you smoke cigarettes, it may contribute to widening milk ducts. It can also cause inflammation which can contribute to mammary duct ectasia.‌

Nipple inversion. If your nipple sinks in instead of sticking out, it may obstruct your milk ducts underneath. If your nipples were always inverted, this isn’t a cause for concern. However, if your nipples began inverting recently, talk to your doctor about the possibility of a more serious condition.

When you have mammary duct ectasia, you may not exhibit any symptoms. If you do, they can include:

  • Thick discharge that can range from white to green or black – it may come from one or both nipples, depending how many ducts are clogged
  • Tender nipples and areola that are sensitive to touch even if you don’t have pain 
  • Redness near the sight of the clogged duct 
  • A lump that you can feel under your skin
  • Thickening of your outer skin at the sight
  • Inverted nipple near the duct
  • A breast infection called mastitis‌

‌Usually, these symptoms go away on their own. However, if you suspect that you have an infection, talk to your doctor. This is especially important if:

  • The redness is persistent
  • Your pain is worsening
  • You have a fever
  • Your breast is swelling‌
  • Any of the symptoms are spreading

Because mammary duct ectasia may not present with symptoms, it may be diagnosed during a breast exam for other concerns. If you do notice a lump on your breast that concerns you, your doctor may request that you complete a mammogram to be safe.‌‌

If the tissue gets thick enough to cause a hard lump under the skin, it may appear as breast cancer on a mammogram or other imaging test. Your doctor may want to take a small sample of breast tissue from the affected area for a biopsy. A biopsy is completed using a small needle inserted into the lump to extract a tissue sample.

Because mammary duct ectasia is benign, biopsy results may not reveal a problem. If the lump is anything other than mammary duct ectasia, your doctor will know based on the results.

Mammary duct ectasia often improves without the need for treatment. You can use a warm compress to soften the tissue or allow hot shower water to hit the area so it can loosen and drain.‌

If the pus is trapped for too long, it can develop bacteria and become infected. If this happens, seek immediate medical treatment. The onset of mastitis symptoms happens quickly and often feels like the flu. You may have a fever, body aches, and overall weakness.‌

While a mammary duct ectasia lump may be tender or slightly painful, mastitis can spread and feel much worse. After completing a physical exam, your doctor may prescribe an antibiotic to treat the infection. They may also recommend an over-the-counter medication to alleviate pain and reduce inflammation.