Fibroadenomas of the Breast

A common noncancerous (benign) breast lump

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Breast fibroadenomas are benign (noncancerous), painless breast lumps. Often described as moveable, round, rubbery, and smooth, fibroadenomas affect one in four premenopausal people.

Fibroadenomas are often triggered by hormonal changes such as birth control pills or pregnancy. They are often first discovered during a breast self-exam and diagnosed using imaging studies and biopsy.

Most fibroadenomas shrink on their own over time. Treatment is unnecessary unless they are large, fast-growing, or cause bothersome symptoms.

This article explains what you need to know about breast fibroadenomas, how they are diagnosed, and what to do about them.

Quick facts about breast fibroadenomas.
Brianna Gilmartin / Verywell

Fibroadenoma Symptoms

Typically, the only symptom of a fibroadenoma is a small lump in the breast that is:

  • Firm
  • Movable
  • Round
  • Rubbery
  • Smooth

Fibroadenomas may feel tender or painful, especially right before your period.

Most fibroadenomas are between 1 and 5 centimeters in diameter (0.39 inches to nearly 2 inches), but large fibroadenomas can be the size of a small lemon—about 15 centimeters (5.9 inches).

Fibroadenomas change in size during your menstrual cycle due to varying hormone levels. A fibroadenoma may become more noticeable or shrink to the point where it is not easily detected.

What Are Breast Mice?

Fibroadenomas are sometimes referred to as “breast mice.” They are so moveable they seem to run away from your fingers.

What Causes Fibroadenomas?

The exact cause of fibroadenomas is unknown. They appear to seem influenced by estrogen because they occur most often in premenopausal people and shrink or disappear after menopause.

Risk Factors

Fibroadenomas are most common in people with a uterus between 15 and 30 years old. Risk factors for developing a fibroadenoma include:

  • Estrogen therapy
  • Hormonal contraception, especially when started before age 20
  • Pregnancy

When to See a Healthcare Provider

Any breast lump should be evaluated by a healthcare provider. If you notice a lump during your monthly breast exam, in the shower, or any other time, having it checked out is essential.

How Breast Fibroadenomas Are Diagnosed

A fibroadenoma may first be discovered on physical examination or during a routine screening mammogram, which often leads to additional testing.

Mammogram

On a mammogram, fibroadenomas appear as round or oval smooth-edged masses. The outline will be clearly defined, not blurry, and not invade the adjacent spaces.

Sometimes they are accompanied by coarse calcifications (calcium deposits). Fibroadenomas can look like cysts or well-contained tumors.

Ultrasound

Breast ultrasound is used to evaluate breast lumps. On ultrasound, a fibroadenoma will be easier to distinguish from other tissue because of the way it responds to sound waves.

Fibroadenomas will appear as a dark area with a definite outline. It will look homogeneous (the same throughout), round or oval, and may have smooth-edged bumps.

3D Mammogram

Your doctor may also order digital breast tomosynthesis (DBT), a specialized form of mammography that creates 3D images of the breast and allows a more detailed evaluation than a regular mammogram.

Biopsy

While imaging tests may suggest a fibroadenoma, the conclusive diagnostic test is usually a breast biopsy, a procedure to remove a sample of tissue for examination in a lab.

Different types of biopsy procedures include:

  • Core-needle biopsy, which uses a needle to extract tissue samples
  • Fine-needle aspiration, similar to a core-needle biopsy
  • Open biopsy, a surgical procedure in which a cut is made in the skin to extract sample tissue

The type your healthcare provider chooses will depend on the characteristics of the lump, its location, and other factors. In you have an increased risk for breast cancer, your healthcare provider may strongly recommend surgical removal.

As with any biopsy, breast biopsies carry a risk of a false-negative result; that is, the test detects no cancer when cancer is actually present. This is because a breast biopsy may only sample one part of a lump and could miss the cancerous portion.

For this reason, you should continue routine breast cancer screening even if you have had a benign biopsy.

Types of Fibroadenoma

Your healthcare provider will also be able to identify the type of fibroadenoma you have. Breast fibroadenomas come in two different types:

  • Simple: Most fibroadenomas are the simple type; they are more common in younger people. There’s usually just one mass in the breast, with a definite border and very uniform cells. A simple fibroadenoma does not raise your risk for breast cancer.
  • Complex: Complex fibroadenomas are more common in women over 35. Under a microscope, a complex fibroadenoma shows signs of rapidly dividing cells (hyperplasia) with an abnormal appearance.

Can Fibroadenomas Become Cancerous?

No, fibroadenomas are benign and cannot turn into cancer. Simple fibroadenomas do not carry an increased risk of breast cancer. Complex fibroadenomas are associated with a slightly higher breast cancer risk, however, studies show complex fibroadenomas are more common in people with other breast cancer risk factors.

Breast Fibroadenoma Treatment

Fibroadenomas are considered benign and do not need always need treatment. They are responsive to female hormones, may enlarge during pregnancy or with estrogen therapy, and shrink or disappear after menopause.

Masses that are large, fast-growing, or cause symptoms can be removed with surgery or another medical procedure.

Watch and Wait

Since fibroadenomas are not always troublesome and sometimes shrink on their own, keeping an eye on their progress is the least invasive way to handle them.

If a fibroadenoma causes pain, over-the-counter pain medications and applied heat can usually help.

Laser Ablation

In your surgeon's office, an ultrasound-guided laser device destroys the fibroadenoma, leaving behind only a tiny scar, no sutures, and no change in breast shape. You don't need general anesthesia, and it's usually an outpatient procedure, which means no hospital stay.

Cryoablation

Cryoablation is a fast, efficient way to freeze a fibroadenoma. In one office visit, the healthcare provider freezes the lump so that healthy tissue can take over. This procedure takes less than 30 minutes and results in a tiny scar.

Radiofrequency Ablation (RFA)

This is a way to remove fibroadenomas without resorting to a lumpectomy. Using local anesthesia and ultrasound guidance, a 6- to 8-millimeter (about 1/4 inch to nearly 1/3 inch) cut is made above the fibroadenoma.

Through this cut, a surgical wand is inserted and then tipped by a knife heated by radiofrequency current. This helps cut through the breast tissue without causing much bleeding. Once it reaches the target, small wires and robotic arms capture the fibroadenoma and extract it.

Vacuum-Assisted Excision

Breast biopsy systems can now be used as a primarily noninvasive way to remove small fibroadenomas. In less than an hour, and under local anesthesia, a 6-millimeter (1/4 inch) cut is made over the fibroadenoma. Then, with ultrasound guidance, a probe is threaded into the lump, which vacuums out sections of the tissue. Recovery is quick, and your scar will be quite small.

High-Frequency Focused Ultrasound (HFU)

This relatively new treatment has been used for fibroadenomas and, sometimes, even breast cancer. HFU appears to cause the selective destruction of deep tissues without damaging surrounding healthy tissue.

Lumpectomy

Surgical removal can be done if you're worried about a fibroadenoma. Depending on the relative size of the lump and your breast, a lumpectomy may cause a change in your breast's size or shape.

New fibroadenomas may grow in the area of the first lump, so surgery does not guarantee that you'll never have another fibroadenoma. On the other hand, your fibroadenoma can be carefully examined by a pathologist to ensure your diagnosis is correct.

Summary

Breast fibroadenomas are the most common type of noncancerous (benign) breast tumor. Often found in premenopausal women during a breast self-exam, they can also be detected on imaging with mammography or ultrasound. A biopsy is the only way to ensure that a breast lump is a fibroadenoma.

Most fibroadenomas are considered simple and are not associated with an increased risk of breast cancer. Some fibroadenomas are considered complex because their cells look unusual under a microscope. Women with complex fibroadenomas have an increased risk of developing breast cancer and may require careful monitoring for signs of developing cancer.

Proven fibroadenomas may not need treatment unless they are large, fast-growing, or cause bothersome symptoms. Various ablation techniques can be used to shrink or destroy problematic lumps. Very large fibroadenomas may need to be surgically removed. 

12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Rony Kampalath, MD
Rony Kampalath, MD, is board-certified in diagnostic radiology and previously worked as a primary care physician. He is an assistant professor at the University of California at Irvine Medical Center, where he also practices. Within the practice of radiology, he specializes in abdominal imaging.

Originally written by Pam Stephan