What Are Breast Cysts?

Here's What You Need to Know About Breast Cysts and Mammograms

A radiologist studies mammograms.
A radiologist studies mammograms. Ben Edwards/Getty Images

Breast cysts are one of the findings that can be seen on your mammogram. These are benign, fluid-filled masses that can appear in your breast tissue. They may be large enough to be felt or too small to detect other than on a scan. They can appear alone or in groups and often they will occur in both breasts.

Breast cysts are very commonly detected by mammography. Cysts are not usually associated with breast cancer and they may need no treatment.

They can be watched and may go away on their own or they may be drained with a fine-needle aspiration.

Squishy Lumps Felt During Breast Self Exam

A breast cyst can be felt when you are doing a breast self-exam. It will feel smooth and squishy, and will have some “give” to it, like a water balloon. These might be painful if they are large and are pressing on some tender area. You may only feel them or feel pain from them just before your menstrual period begins. Breast cysts are most common in women aged 35-50 who are in perimenopause. They can also appear in women who are taking menopausal hormone therapy.

Cysts Show Up on Your Mammogram

A mammogram will show dense areas of tissue. If a cyst or a solid area (fibroadenomas or a tumor) appears on a mammogram, a radiologist sees those as dense masses. A lump that is smooth and round with a clear, defined edge is often a benign cyst. The size, shape and edges are what the radiologist will look at to recommend any further imaging tests or biopsy.

Dealing with Dense Masses

If your radiologist finds a dense mass on your mammogram, and thinks it may be a cyst, the next step is to perform an ultrasound on it. An ultrasound sends sound waves through breast tissue, which will pass through a fluid-filled spot. Solid masses will reflect sound waves, and will make a different image on the ultrasound than will a cyst.

Causes of Breast Cysts

During your regular menstrual cycle, your breast produces and absorbs fluid in response to hormonal changes. Excess estrogen may stimulate the breast to make more fluid than is absorbed and subsequently this fluid may collect in small sacs or pockets. Many of us have small cysts without realizing it, or without being bothered by any pain or bumpiness. These usually doesn’t require any treatment, but they can be drained if they are is uncomfortable.

When Do Cysts Appear?

Cysts are most common in women who are 35 to 50 years old and are perimenopausal. If you’re taking hormone replacement therapy (HRT) you may also experience breast cysts. Breast oil cysts may occur after breast surgery, breast reconstruction, an injury to your breast, or they may grow spontaneously.


Understanding Breast Changes: A Health Guide for Women, National Cancer Institute, updated April 23, 2015.

Fibrosis and simple cysts, American Cancer Society, updated 06/10/2015.

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