Breast Cyst

Medically Reviewed By William C. Lloyd III, MD, FACS
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What is breast cyst?

A breast cyst is a fluid-filled sac in the breast tissue. Women can have just one cyst, many cysts in the same breast, or breast cysts in both breasts. The tendency to develop breast cysts and other benign breast conditions often runs in families. Cysts in breast tissue are common in premenopausal women and those approaching menopause. They tend to grow or become noticeable around your monthly period and resolve afterwards. Although less common, breast cysts can also occur in women who have gone through menopause.

Breast cysts are usually not cancerous, but they can cause women concern because they feel like lumps. Some women have naturally lumpy breasts and are more prone to developing cysts. These fibrocystic changes make breast tissue more dense, which can make it harder to read mammograms and spot cancerous changes. It’s important for women with fibrocystic breasts to be familiar with the normal feel of their breasts. It will help them notice changes that their doctor may need to investigate further.

Most cysts do not require treatment, but your doctor should still evaluate any change in your breasts. Seek prompt medical care if you notice a lump in your breast. You may need tests to find out whether the lump is a cyst or something more concerning. Some cysts can also grow and become painful. Seeing your doctor early can put your mind at ease and treat the problem if necessary.

What are breast cyst symptoms?

Usually, the main signs of breast cyst are a lump or lumps in the breast. Here are some other characteristics to keep in mind:

  • The lump is typically smooth, round and moveable—it is not fixed or stuck in the breast tissue.
  • The breast cyst may or may not be painful.
  • It’s common for breast cysts to grow and become tender in the days leading up to your period.
  • Breast cysts often shrink and feel better after your period. Sometimes, women notice nipple discharge with these hormonal shifts.

Always see your doctor if you find a lump or notice other changes in your breasts. Your doctor may be able to tell from a simple ultrasound test whether the lump is fluid-filled or solid. Fluid-filled lumps are likely to be simple cysts that are not cancerous. Solid masses or mixed solid-and-fluid cysts are more concerning. Cysts with both solid and fluid elements are complex cysts. These cysts usually require a biopsy to find out whether they are cancerous.

Sometimes, doctors need to withdraw fluid from the cyst to make a diagnosis. This is a fine-needle aspiration. If the cyst disappears when withdrawing the fluid, it is a simple cyst. If the fluid is bloody or the cyst remains after the fluid is gone, your doctor will send the fluid to a lab for analysis. If your doctor can’t withdraw any fluid, you will need other tests, such as a diagnostic mammogram or breast biopsy.

What causes breast cysts?

A breast cyst develops when fluid accumulates in the glandular tissue of the breast. Breast glands are the milk-producing components of the breast. Sometimes, cysts are too small to feel, but your doctor can see them on a mammogram. These are microcysts. When cysts fill with enough fluid that they are large enough to feel, they are macrocysts. Macrocysts can grow to be quite large, up to two inches in diameter.

Doctors don’t know exactly why breast cysts form and grow. Evidence seems to suggest hormones, especially estrogen, play a role in breast cyst development.

What are the risk factors for breast cysts?

Some women are more prone than others to developing breast cysts and having lumpy breasts. There is not a lot of information about factors that increase the risk of breast cysts. In general, benign breast conditions, including breast cysts, tend to run in families. If other women in your family have dense or cystic breast tissue, you may be more likely to have the same issues.

Reducing your risk of breast cysts

Because doctors don’t really understand why breast cysts develop, there isn’t much you can do to prevent them. Some research suggests cutting out caffeine may help, but the link isn’t strong. If you’re concerned about breast cysts, talk with your doctor about your risk.

How are breast cysts treated?

Most breast cysts don’t cause problems and don’t require treatment. Many cysts will go away with time. For large or bothersome cysts, your doctor may recommend draining them. This breast cyst treatment involves numbing the area and using ultrasound to guide a needle into the cyst. Your doctor withdraws all the fluid and the cyst collapses. This usually provides relief. However, cysts can refill with fluid and return with time. Your doctor may drain it again or recommend surgery to remove it if it continues to recur and cause problems.

Hormone therapy to regulate menstruation can help reduce cyst development in premenopausal women. Doctors usually reserve this option for severe cases. This includes women with frequent symptoms and those who continue to develop new cysts. Once a woman goes through menopause, stopping hormone therapy will help control breast cysts.

What are the potential complications of breast cysts?

Simple cysts usually do not cause long-term problems. They do not increase a woman’s chance of breast cancer by themselves. However, having many cysts and fibrous changes in the breast tissue can make it more difficult to spot cancer on a mammogram. If you have fibrocystic or dense breasts, ask your doctor about supplemental screening exams to see if they are right for you. This can include getting 3D mammograms or adding breast ultrasound or MRI (magnetic resonance imaging) tests to a standard mammogram screening.

Complex cysts can be more problematic in the long term. It is possible for them to contain cancerous cells or to put you at risk for developing cancer in the future. The biopsy results will give your doctor information about this likelihood.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Aug 29
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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  6. Fibrosis and Simple Cysts in the Breast. American Cancer Society.