Fibroadenomas are the most benign breast tumors that arise in young women. Histological examination of these lesions usually reveals lobular hyperplasia. Presents as a small, well-defined, mobile mass with a rubbery or firm consistency that can increase in size depending on estrogen levels and does not increase the risk of breast cancer. The diagnosis of fibroadenomas is based on physical findings and ultrasonography. Management is based on regular checkups to monitor growth.

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Image: Mammography showcasing a fibroadenoma by Menezes GL, van den Bosch MA, Postma EL, El Sharouni MA, Verkooijen HM, van Diest PJ, Pijnappel RM. License: CC BY 2.0 Edited by Lecturio.

Definition, Epidemiology, and Etiology


  • Benign breast masses
  • Composed of fibrous and glandular tissue


  • Most common in women < 35 years of age
    • Peak incidence: 15–35 years
  • Most common benign tumor of breast
  • Accounts for half of all breast biopsies
  • Does not increase the risk of developing malignant breast cancer.


  • Unknown
  • Unlikely to be hereditary
  • Negative correlation with smoking tobacco
  • Relationship has been established with estrogen
    • Increases in size during pregnancy, lactation, cyclically with menstruation, and with the use of oral contraceptives
    • Regresses after menopause

Video Gallery

Fibroadenoma by Carlo Raj, MD

Breast Masses in Adolescent Girls: Fibroadenoma & Mastitis by Brian Alverson, MD

Clinical Presentation

  • Generally asymptomatic
  • Solitary lesion in 80% of cases
  • 20% of cases consist of multiple fibroadenomas occurring in the same breast or bilaterally.
  • Small, spherical, well-defined, mobile mass with a rubbery or firm consistency
  • Diameter of 3–10 cm that causes breast asymmetry (usually < 3 cm)
  • Usually found in the upper-outer quadrant of the breast
  • Cyclic increase in size due to sensitivity to estrogen 
  • Other types of fibroadenomas
    • Juvenile fibroadenomas
      • Usually occur in African American patients ages 10–18
      • Rapid increase in size 
      • May cause skin ulceration
    • Giant fibroadenomas
      • Histologically typical fibroadenomas over 10 cm in size
      • Excision is recommended
    • Complex fibroadenomas
      • Proliferative pathologic changes
      • Associated with a slightly increased risk of cancer
      • Management is controversial

Diagnosis and Management


  • Ultrasonography: well-defined mass with smooth and regular boundaries and a weak echo signal
    • 25% of cases have irregular borders → biopsy to confirm benignancy
  • Mammogram or MRI: regular boundaries and popcorn-like calcifications
  • Fine needle aspiration (method of choice for biopsy): fibrous and glandular tissue with clusters of spindle cells, antler horn clusters, and honeycomb sheets


  • Regular check-ups in cases confirmed to be benign (“wait-and-see” approach)
  • Cryoablation for small but symptomatic fibroadenomas 
  • Surgical resection for cases of juvenile and giant fibroadenomas, irregular boundaries, and patients with personal or family history of breast cancer

Clinical Relevance

The following conditions are differential diagnoses of fibroadenomas.

  • Galactocele: retention cyst within the mammary gland containing milk, which presents as a palpable, firm mass in the subareolar region.
  • Breast abscess: accumulation of pus within the mammary gland. Usually associated with lactational mastitis. Presents as a unilateral and fluctuant mass within a painful, erythematous, and edematous breast.
  • Intraductal papilloma: benign mass with a papillary configuration of breast stroma and epithelium within a breast duct, which presents as a solitary mass found close to or behind the nipple with bloody nipple discharge.
  • Phyllodes tumor: fibroepithelial tumor similar to fibroadenomas, usually characterized by rapid growth. 
  • Fibrocystic changes of the breast: term that refers to the changes that happen to breast tissue while a woman ages. The normal histologic appearance of predominant ducts, lobules, intralobular stroma, and interlobular stroma is replaced by fibrous tissue and cystic formation.
  • Mastitis: inflammation of the mammary gland tissue, which can be lactational or non-lactational. It is most common in women within childbearing age.
  • Fat necrosis of the breast: usually due to breast injury. As the damaged breast tissue is repaired it is replaced by scar tissue. However, some fat cells may have a different response and form what is known as oily cysts.
  • Breast cancer: also known as mastocarcinoma, is a malignant tumor of the mammary gland. The two most common breast cancer types are ductal carcinoma and lobular carcinoma.
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