Fibroadenomas are the most common benign tumor of the female breast and the most common breast tumor in adolescent and young women. The tumors are well-circumscribed, mobile, and unencapsulated, with a rubbery or firm consistency. Fibroadenomas are hormonally responsive, so they may increase in size during pregnancy and usually regress after menopause. Histologically, fibroadenomas are composed of a biphasic proliferation of both glandular and stromal elements. Fibroadenomas are associated with a slightly increased risk of carcinoma, with a somewhat higher risk if so-called “complex” features are present. Diagnosis is based on physical findings and ultrasonography. Management is based on regular checkups to monitor growth.

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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 the breast, and the most common tumor in young women
  • Accounts for half of all breast biopsies
  • Only a slightly increased risk of developing malignant breast cancer, with a somewhat higher risk if “complex” features are present:
    • Cysts > 0.3 cm
    • Sclerosing adenosis
    • Epithelial calcifications
    • Papillary apocrine change


  • Unknown
  • Unlikely to be hereditary
  • Negative correlation with tobacco smoking
  • A 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

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 changes in size related to the menstrual cycle due to sensitivity to estrogen 
  • Other types of fibroadenomas:
    • Juvenile fibroadenomas
      • Usually occur in African American patients aged 10–18 years
      • Rapid increase in size 
      • May cause skin ulceration
    • Giant fibroadenomas
      • Histologically typical fibroadenomas > 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 magnetic resonance imaging (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
    • 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

Differential Diagnosis

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: uncommon fibroepithelial tumor similar to a fibroadenoma but requiring complete surgical excision with clean borders because of its malignant potential. The tumors are categorized into benign, borderline, and malignant types. Histologically, these tumors have stromal overgrowth with increased mitotic activity, with the borderline and malignant tumors showing infiltrative borders. 
  • Fibrocystic changes of the breast: refers to the common changes that happen to breast tissue as a woman ages, causing a “lumpy-bumpy” breast in the more pronounced expressions of the condition. These changes can be non-proliferative (cysts, fibrosis, adenosis) or proliferative (epithelial proliferation, sclerosing adenosis, papilloma), with or without atypia. Atypical hyperplasia has a moderately increased risk of carcinoma.
  • Mastitis: inflammation of the mammary gland tissue; can be lactational or non-lactational. Mastitis is most common in women of childbearing age.
  • Fat necrosis of the breast: usually due to breast injury, which often goes unnoticed. 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 are known as oily cysts.
  • Breast cancer: malignant tumor of the mammary gland. The 2 most common histological types of breast cancer are ductal carcinoma and lobular carcinoma.


  1. Vinay K, Abbas A, Aster J. Robbins & Cotran Pathologic Basis of Disease. 2020, 10th Edition, Elsevier.
  2. Sabel MS. Overview of benign breast disease. UpToDate. Retrieved on August 28, 2020, from
  3. Rohan, T. E., & Miller, A. B. (1999). A cohort study of cigarette smoking and risk of fibroadenoma. Journal of Epidemiology and Biostatistics, 4(4), 297–302.

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