Fibroadenomas of the Breast

Fibroadenomas of the breast are benign tumors:
- Composed of stromal and epithelial elements:
- That are commonly seen in young women
- Multiple or complex fibroadenomas:
  - May indicate a slightly increased risk for breast cancer:
  - The relative risk of breast cancer in patients with such fibroadenomas:
    - Is approximately twice that of patients of similar age without fibroadenomas
- A patient’s age determines the preferred imaging method:
  - In general, ultrasonography (US) is preferred:
  - If a palpable mass is found
  - If a patient is younger than 30 years
  - If the patient is pregnant
  - Mammography and US are both useful if the patient has:
  - A palpable mass
  - Is older than 30 years
  - Is not pregnant
  - In patients younger than 30 years:
  - The most appropriate modality is ultrasound:
    - Because the patient is spared radiation exposure and because the likelihood for fibroadenoma is high
  - Mammography is not indicated as the primary imaging study in women younger than 30 years:
  - Unless high-risk factors are present
  - Computed tomography (CT) scanning:
  - Is not initially indicated for assessing a palpable lump in a woman in women younger than 30 years:
    - Because of radiation exposure
    - The inability of CT to demonstrate micro-calcifications
    - The lack of specificity in the findings
  - Magnetic resonance imaging (MRI):
  - Is not initially indicated for assessing a palpable lump in women younger than 30 year:
    - Mainly because of its high cost and the high likelihood of false-positive findings
  - Positron emission tomography:
  - Is expensive and is not universally available
  - On mammograms:
  - Fibroadenomas typically appear as:
    - Circumscribed oval or round masses:
      - Which occasionally have coarse calcifications
  - On ultrasonograms:
  - Fibroadenomas appear as:
    - Circumscribed, homogeneous, oval, hypoechoic masses:
      - That may have gentle lobulations
      - A smooth, thin, echogenic capsule
      - Variable acoustic enhancement; and homogeneity
  - On MRI:
  - Fibroadenomas typically appear as smooth masses with high signal intensity on T2-weighted images and enhancement with the administration of gadolinium-based contrast agent
  - Fibroadenoma:
  - Is a common benign breast lesion:
    - Results from the excess proliferation of connective tissue
  - Fibroadenomas characteristically contain both:
    - Stromal and epithelial cells
  - Epidemiology:
  - They usually occur in women:
    - Between the ages of 10 and 40 years
    - It is the most common breast mass:
      - In the adolescent and young adult population :
      - Their peak incidence is between:
      - 25 and 40 years
  - The incidence decreases after 40 years
  - Clinical presentation:
  - The typical presentation is in a woman of reproductive age:
    - With a mobile palpable breast lump:
  - Due to their hormonal sensitivity:
    - Fibroadenomas commonly enlarge during pregnancy and involute at menopause:
      - Hence, they rarely present after the age of 40 years
  - The lesions are well defined and well-circumscribed clinically and the overlying skin is normal
  - The lesions are not fixed to the surrounding parenchyma and slip around under the palpating fingers:
    - Hence the colloquial term a breast “mouse”
  - Pathology:
  - A fibroadenoma is a type of adenomatous breast lesion:
    - It contains epithelium:
      - Has minimal malignant potential
  - Multiple fibroadenomas occur in:
    - 10% to 15% of patients:
      - Patients with multiple fibroadenomas:
      - Tend to have a strong family history of these tumors
    - They are assumed to be:
      - Aberrations of normal breast development (ANDI) or the product of hyperplastic processes:
      - Rather than true neoplasms
  - Fibroadenomas can be stimulated by estrogen and progesterone:
    - Some fibroadenomas also have receptors and respond to:
      - Growth hormone and epidermal growth factor
  - When found in an adolescent girl:
    - The term juvenile fibroadenoma is more appropriate
  - Location:
  - Although they can be located anywhere in the breast:
    - There may be a predilection for the upper outer quadrant
  - Associations:
  - Cyclosporin use o Cowden syndrome
  - Radiographic features:
  - Mammography:
    - Fibroadenomas have a spectrum of features:
      - Well-circumscribed discrete oval mass hypodense or isodense to the breast glandular tissue
      - Mass with macro-lobulation or partially obscured margin
      - Involuting fibroadenomas in older, typically postmenopausal patients may contain:
      - Calcification:
        Often producing the classic, coarse popcorn calcification appearance
        In some cases the whole lesion is calcified
        Calcification may also present as crushed stone-like micro-calcification:
        Which makes differentiation from malignancy difficult
  - Breast ultrasound:
    - Typically seen as a well-circumscribed, round to ovoid, or macro-lobulated mass with generally uniform hypoechogenicity
    - Intralesional sonographically detectable calcification:
      - May be seen in approximately 10% of cases
    - Sometimes a thin echogenic rim (pseudo capsule) may be seen sonographically
  - Breast MRI:
    - T1: typically hypo intense or isointense compared with adjacent breast tissue
    - T2: can be hypo- or hyper intense
    - T1 C+ (Gd): can be variable but a majority will show slow initial contrast enhancement followed by a persistent delayed phase (type I enhancement curve)
      - Non-enhancing internal septations may be seen
  - Diagnosis:
  - These lesions are easily biopsied under ultrasound guidance
  - When a lesion has the typical features of a fibroadenoma on ultrasound and there are no clinical red flags:
    - They can be safely followed clinically
  - When lesions enlarge or have atypical imaging findings:
    - Ultrasound-guided core biopsy is a minimally invasive outpatient procedure that will give a diagnosis with virtually no complications
    - There may be a maximum diameter above which a biopsy should be done if no previous imaging is available:
      - The reason for intervention based on size is that a phyllodes tumor may be indistinguishable from a fibroadenoma on ultrasound:
      - A maximum diameter of 2.5 cm may be a useful benchmark for biopsy if you have no previous imaging
    - Interval enlargement:
      - Is an indication for biopsy
- Symptomatic, progressively enlarging masses or atypical presentations:
  - May warrant surgical excision
- If a needle biopsy shows that a mass less than 2 centimeters in size is a fibroadenoma, with no other concerning features:
  - It does not have to be surgically removed
- The patient’s core biopsy pathology demonstrating a fibroadenoma is consistent with the typical imaging findings of a smooth, round, hypoechoic mass:
  - As the biopsy is concordant, no further intervention is needed:
  - Follow-up for reassurance is acceptable
- Treatment and prognosis:
  - They are benign lesions with minimal or no malignant potential
  - The risk of malignant transformation is extremely low:
  - Has been reported to range around 0.0125% to 0.3%
  - Indications for biopsy include:
  - Enlarging lesion
  - Atypical findings on ultrasound
  - A lesion above 2.5 cm and there are no previous studies for comparison
  - Patient peace of mind:
    - Some patients are simply not happy with a palpable mass in the breast without a histological diagnosis:
      - This is a valid and reasonable indication for biopsy

References
- Tan BY, Tan PH A Diagnostic Approach to Fibroepithelial Breast Lesions. Surg Pathol Clin. 2018 Mar;11(1):17-42.
- American Society of Breast Surgeons – benign breast disease. January 8, 2018. Choosing Wisely website. http://www.choosingwisely.org/clinician-lists/asbrs-benign-breast-disease-biopsy-proven-fibroadenomas-smaller-than-2-cm/. Accessed October 17, 2019.