What Causes Fibroadenoma of the Breast?

Medically Reviewed By Faith Selchick, DNP, AOCNP
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Fibroadenoma is a common noncancerous breast lump that can develop in females. It is most likely to affect those ages 14–35 years, but it can occur at any age. The presence of a breast lump can trigger anxiety. However, not all breast lumps are life threatening. Noncancerous breast lumps generally do not pose any significant danger, but some may require medical attention. 

Read on to learn more about breast fibroadenomas, including the causes, diagnosis, and treatment.

Sex and gender exist on a spectrum. This article uses the terms “female” and/or “male” to refer to sex that was assigned at birth. 

Learn more about the difference between sex and gender here.

Types of fibroadenomas of the breast

Female checking her breast
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Fibroadenomas are solid tumors that comprise both epithelial and fibrous connective tissues and appear under the skin of the breast. Microscopic evaluation of lump tissues helps doctors differentiate between the two types of fibroadenoma: simple and complex.

Simple fibroadenomas do not have complex features such as epithelial calcifications, and they are typically not linked to malignant changes. 

Complex fibroadenomas, which tend to affect older females, are generally larger than simple fibroadenomas. They have microscopic characteristics, such as epithelial calcifications and glandular tissue changes. Complex fibroadenomas have a higher risk of malignant changes than simple ones.

Due to this risk, it is important to consult a doctor if you notice any breast lumps.

What causes fibroadenoma of the breast?

Experts are unsure about the exact cause of fibroadenomas but suspect that female hormones may play a role in their growth. Female breast tissues contain both estrogen and progesterone receptors. Some people may have increased sensitivity to these hormones, which causes excessive proliferation of breast connective tissues.

The fact that fibroadenomas typically grow during pregnancy and shrink during menopause supports the theory that hormones play a role. During menopause, the level of female hormones, including estrogen and progesterone, drops significantly. This reduces the growth effect on the breast tissues.

Also, fibroadenomas are generally more common among females who began using birth control pills before the age of 20 years.

Research scientists have also proposed that genetic factors play a role in the formation of breast fibroadenomas. They have discovered that mutation in the MED12 gene is prevalent among females of reproductive age who have developed a fibroadenoma.

What does fibroadenoma of the breast feel like? 

Fibroadenoma of the breast appears as a painless lump. In some cases, the lump is solid. It may feel like a marble or a rubbery mass under your skin. Fibroadenomas typically feel round with defined borders and high mobility. You may have one or multiple lumps in one or both breasts.

In some cases, you will be unable to feel a fibroadenoma that is small and highly mobile. Imaging tests are critical in identifying these types of fibroadenomas. 

Learn about the warning signs of breast cancer.

How do doctors diagnose fibroadenoma of the breast? 

Generally, a doctor will start by taking a clinical history and then conducting a breast examination. They may order a biopsy to confirm a diagnosis of breast fibroadenoma.

Clinical evaluation of fibroadenoma

The doctor will typically consider your age and family history. Females with breast fibroadenoma and a family history of breast cancer in first-degree relatives require regular monitoring and clinic follow-ups.

During the follow-up visits, the doctor will typically examine the lumps for any malignant features. Many females with fibroadenoma typically become aware of it when they feel a painless lump in the upper outer quadrant of the breast. However, the lump may appear in any area of the breast.

During a physical examination, the following lump features usually suggest a breast fibroadenoma:

  • mobile
  • solitary
  • non-tender or painless
  • solid lump with rubbery consistency and regular borders

Subsequently, the doctor may order radio imaging tests to identify and characterize the number and size of the lumps. 

Investigation of fibroadenoma

Some of the common investigations that hospitals use for diagnostic purposes are:


A mammogram is a special breast X-ray that helps doctors visualize and evaluate breast lumps or suspicious masses in females older than 35 years

Mammographic features that suggest a breast fibroadenoma include:

  • isolated regions filled with masses with smooth round edges distinct from other breast tissues
  • oval masses that have well-defined borders and consist of tissue that is less dense than or similar in density to the surrounding tissue
  • masses with lobulation
  • masses that contain calcification, in some fibroadenomas in older females

Breast ultrasound

Breast ultrasound uses sound waves to detect the features of breast fibroadenomas in younger females. Doctors typically use ultrasound scans for females younger than 35 years.

A breast ultrasound scan helps distinguish solid masses from cystic ones.

Breast biopsy

A breast biopsy is a minimally invasive clinical procedure in which a medical professional removes a sample of breast tissue for microscopic examination. The radiologist or surgeon uses a radio imaging device such as an ultrasound scan as a guide during the procedure. They excise, or cut off, part of the breast lump using a special needle and send the sample to the laboratory for microscopic evaluation.

Doctors typically only recommend this procedure if they believe that there is a risk of breast cancer.

How do you treat fibroadenoma of the breast?

Most cases of fibroadenoma of the breast require only close monitoring and evaluation through regular clinic follow-up visits. Fibroadenomas in most females typically shrink and disappear without any treatment. With age, the concentration of female hormones drops, causing breast fibroadenomas to contract.

However, some fibroadenomas of the breast continue to grow and may affect other normal breast tissues. In such cases, breast surgery may be an option. The surgeon may decide to use an excisional biopsy technique or a freezing technique called cryoablation.

It is important to note that even after the surgery, there is a risk of recurrence.  

Learn more about breast lumps.


Fibroadenomas of the breast are noncancerous tissues that present as solid and painless breast lumps in females. They are more common in young females and typically do not pose any health dangers.

Female hormones may play a crucial role in the development of fibroadenomas.

A doctor will diagnose a breast fibroadenoma after a thorough clinical examination and radio imaging tests, such as a breast ultrasound scan or mammogram. A breast ultrasound scan is suitable for women less than 35 years of age, while a mammogram is ideal for women older than this.

 Regular checkups are important in most cases of breast fibroadenomas, especially when doctors decide that treatment is unnecessary. Breast fibroadenomas that are growing rapidly may require surgery.

If you have a breast fibroadenoma, regular clinic visits for breast exams or imaging tests are critical to ensure that the lump is not growing.

It is essential to consult a doctor about any changes or lumps in your breasts.

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Medical Reviewer: Faith Selchick, DNP, AOCNP
Last Review Date: 2022 Aug 23
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