Can Fibroadenomas Turn Into Breast Cancer?

What are fibroadenomas?

Fibroadenomas or Breast Cancer Exam
Although it is rare, complex fibroadenomas and phyllodes tumors have a chance to develop into malignant breast cancer.

A fibroadenoma is the most common type of benign, non-cancerous lump of the breast. It usually occurs in young women between the ages of 15 and 40. They may also arise during pregnancy or breastfeeding. They usually do not cause complications and can be treated easily.

Fibroadenomas should not be confused with fibroids. A fibroid is a noncancerous mass that occurs in the uterus.

What are the types of fibroadenomas?

Fibroadenomas are classified into five types based on the physical characteristics and how it appears under the microscope.

  • Simple fibroadenomas: They are small and appear uniform when examined under a microscope.
  • Complex fibroadenomas: These are bigger and tend to affect older women. They increase in size rapidly.
  • Juvenile fibroadenomas: These are the most common type of breast lump occurring in young girls and adolescents between the ages of 10 and 18 years. They tend to grow to a large size. However, these usually shrink over time and may even disappear.
  • Giant fibroadenomas: Giant fibroadenomas can grow to a size larger than two inches. 
  • Phyllodes tumor: This tumor arises from another kind of tissue in the breast. It needs to be monitored. Most doctors recommend excising it.

Can fibroadenomas turn into breast cancer?

Although it is rare, complex fibroadenomas and phyllodes tumors have a chance to develop into malignant breast cancer. Hence, timely medical attention and management of the tumor are highly recommended.

What are the causes of fibroadenoma?

The exact causes of fibroadenomas are not known. It is believed to be related to changes in reproductive hormones because fibroadenomas tend to occur in premenopausal women. 

Fibroadenomas have been found to change characteristics with hormonal variations. They may increase during pregnancy, breastfeeding, and use of hormone therapy. They may shrink after menopause or when hormone levels decrease e.g., withdrawal of hormone therapy.

How is a fibroadenoma different from a cancerous lump?

Fibroadenomas are generally asymptomatic and hence usually discovered on routine examination by self or the doctor. Common clinical features of fibroadenomas are:

  • Fibroadenomas are painless
  • They are usually small, between one and two centimeters
  • They are round with smooth edges 
  • The lump is mobile and can be moved around within the breast tissue. Hence, fibroadenomas are also called “breast mice.”
  • It feels firm (similar to the tip of the nose) and rubbery.
  • Multiple lumps may be seen in one or both breasts.
  • It is slow growing. 
  • Size may increase during pregnancy, hormonal therapy, or breastfeeding (breastfeeding is not affected).
  • Larger fibroadenomas may cause breast asymmetry, causing aesthetic concerns.
Differences between a benign fibroid lump and cancerous lump
Fibroadenoma Cancer
Seen in premenopausal women Seen in postmenopausal women
Feels round, firm, rubbery with smooth edges Feels hard with parts of firm areas
Typically painlessl Painless in the early stages. Pain may develop in the later stages due to complications
Freely mobile within the breast Usually fixed to underlying breast tissue or skin, hence not mobile
Skin over the lump is normal and not involved Skin involvement leads to puckering and redness of the skin, giving an orange peel appearance
Nipple is not involved Nipple may be involved, causing change in the shape of the nipple. Usually appears pulled in. nipple discharge and bleeding may be present
Usually slow glowing Fast growing and can spread to other organ systems
Can be managed conservatively using a “wait and watch” approach Requires urgent medical and surgical care


A lump in the breast is almost always cancer. See Answer

How are fibroadenomas diagnosed?

The diagnosis involves detailed history taking and physical examination by a doctor. Diagnostic tests like ultrasonography, mammogram, or biopsy may be required to confirm the diagnosis and rule out other types of lumps.

Should fibroadenomas be removed?

Fibroadenomas can be managed conservatively if they are asymptomatic. Regular follow-up and routine self-examination may be required to monitor the size and detect any changes in the characteristics of the lump. Sometimes fibroadenomas shrink and even disappear on their own with age, menopause, postpartum, and when reproductive hormone levels decrease.

Surgical removal of fibroadenoma is indicated in case of the following:

  • Sudden increase in the size of a long-standing lump,
  • Rapidly growing lump,
  • Breast asymmetry,
  • Giant fibroadenomas: Because their large size can create breast asymmetry and cause the affected breast to press on the other.
  • Complex fibroadenomas and phyllodes tumor: Because they rapidly increase in size and have the possibility to turn cancerous.

Regular follow-up may be required after surgery. 


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