A fibroadenoma is a common type of benign or noncancerous lump that can develop in the breast. Larger fibroadenomas may feel like a hard or rubbery marble that moves around under the skin.

People may also refer to a fibroadenoma as a “breast mouse.”

A person with a fibroadenoma is unlikely to experience any symptoms other than the lump itself. A fibroadenoma is highly unlikely to lead to cancer and rarely causes any complications.

This article looks at the causes of fibroadenomas and how doctors diagnose and treat them.

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A fibroadenoma is a benign tumor that can develop in the breast. Doctors do not know why some people develop them while others do not. They are commonTrusted Source in females and rare, but possible, in males.

Fibroadenomas consist of glandular and connective tissue and can vary in size. Some are so small that a person cannot feel them, while others are easy to locate during a self-examination.

If a fibroadenoma is large enough to feel, it might feel like a round or oval marble within the breast. The lump will usually feel firm or rubbery, and a person will be able to move it under the skin.

A person may have one fibroadenoma or many. Fibroadenomas may maintain their size or grow or shrink over time.

Doctors classify fibroadenomas as either simple or complex. According to the American Cancer Society (ACS)Trusted Source, simple fibroadenomas look the same all over when a doctor examines them under a microscope. Complex fibroadenomas are usually larger and have different features.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Learn more.

Doctors do not knowTrusted Source exactly what causes fibroadenomas, but they think genetics and sensitivity to reproductive hormones may play a role.

Breasts comprise:

  • lobules, which are milk-producing glands
  • ducts, which carry milk to the nipple
  • glandular, fatty, and fibrous tissue

Breast Cancer Now (BCN) notes that fibroadenomas develop from a lobule. Ducts and glandular tissue grow over it, forming a solid lump.

A fibroadenoma is not usually painful or tender to the touch. Most people do not experience any symptoms other than the lump.

According to BCN, fibroadenomas may feel tender before a person’s period. They may also get bigger during pregnancy, breastfeeding or chestfeeding, or while taking hormone therapy. Fibroadenomas will usually return to their previous size after hormone fluctuations.

The ACSTrusted Source notes that doctors can detect a fibroadenoma through an initial physical examination if it is large enough. If the doctor suspects a fibroadenoma, they will confirm it using an imaging test, such as a mammogram, an ultrasound, or both.

The doctor may recommend a biopsy to ensure the lump is a fibroadenoma. The individual will receive a local anesthetic, after which the doctor will remove a small sample of the lump to send to a laboratory for testing.

Doctors may recommendTrusted Source the following treatments for fibroadenoma:

Lumpectomy

If a fibroadenoma has any abnormalities, a doctor may recommend surgical removal. In lumpectomy surgery, also called excision biopsy, a doctor will make a small cut in the breast to remove the fibroadenoma.

This procedure can take place under either a local or general anesthetic. The choice will depend on the features of the fibroadenoma and its location in the breast.

According to older 2015 researchTrusted Source, surgery is rarely necessary if the cells of the fibroadenoma appear normal. Surgery could leave scars on the breast, which may interfere with future imaging tests.

The American Board of Internal Medicine recommends that doctors do not surgically remove fibroadenomas smaller than 2 centimeters (cm)Trusted Source. If they are increasing in size or are bothering a person, doctors might recommend surgery.

Vacuum-assisted excision biopsy (VAB)

A VAB is a nonsurgical procedure to remove a fibroadenoma. A doctor will inject a local anesthetic before making a small cut into the skin. They will then insert a probe that connects to a vacuum device that sucks out the fibroadenoma.

A doctor will then send the fibroadenoma tissue for testing at a laboratory. BCN notes that people may experience some pain or bruise in the area after a VAB. Sometimes, the tissue removal may leave a small dent in the breast.

Cryoablation

Cryoablation is another nonsurgical option for fibroadenoma removal. Cryoablation uses liquid nitrogen to freeze and destroy unwanted tissue in the body. Once the cells of the fibroadenoma die, the immune system’s white blood cells clear the dead tissue from the body.

A doctor may use imaging techniques, such as an ultrasound or a CT scan, to help them locate the area to target with cryoablation. They can then insert a probe through a small cut in the skin to reach a fibroadenoma and apply the liquid nitrogen.

Fibroadenomas do not usually cause any complications. It is possible that a person may develop breast cancer out of a fibroadenoma, but this is highly unlikelyTrusted Source. The risk of breast cancer may be slightly higher with complex fibroadenomas than with simple fibroadenomas.

Fibroadenomas are noncancerous and do not usually cause significant problems. They tend to shrinkTrusted Source after menopause.

Fibroadenomas can also change size in response to hormone fluctuations before menopause. If this occurs, a doctor may suggest regular checkups to monitor the changes.

BCN notes that a person should talk with a doctor if they notice any changes in the breasts, regardless of how long after a diagnosis of fibroadenoma these occur.

Healthcare professionals do not know the exact cause of fibroadenoma.

Usually, fibroadenomas shrink and disappear on their own over time. However, a doctor may recommend removing large fibroadenomas that compress other breast tissues.

Healthcare professionals do not recommend people with fibroadenoma avoid eating any particular foods.

TypicallyTrusted Source, a fibroadenoma will stay the same size or shrink and will not affect a person’s life. Some people may not experience symptoms other than a lump, but others may feel pain or tenderness.

Most people with a fibroadenoma will not need surgery to remove it. However, a doctor may recommend nonsurgical treatment, involving a VAB or cryoablation.

Fibroadenoma will rarely lead to breast cancer or cause other significant issues.

However, it is essential that anyone who finds a lump in their breast seeks further medical advice. Identifying a fibroadenoma is straightforward, and a diagnosis can give a person peace of mind and rule out other conditions.