What is a fibroadenoma?

Fibroadenoma: A Benign Breast Lesion

A fibroadenoma is the most common benign breast tumor, typically presenting as a smooth, rubbery, mobile mass that predominantly affects young women under the age of 40. 1

Clinical Characteristics

• Presentation:

  • Smooth, rubbery, mobile mass on palpation
  • Usually painless
  • Typically unilateral
  • Most common in women under 40 years of age
  • May enlarge during pregnancy or hormonal changes 2

• Physical Examination Findings:

  • Well-circumscribed
  • Mobile ("breast mouse" - moves freely within breast tissue)
  • Firm consistency
  • Usually 1-3 cm in diameter, though can be larger

Diagnostic Features

Imaging Characteristics

• Ultrasound: Solid, round, well-circumscribed masses with homogeneous echogenicity, often with:

  • Oval or round shape
  • Abrupt well-defined margins
  • Orientation parallel to the chest wall
  • No posterior acoustic shadowing 3

• Mammography: Well-circumscribed, round or oval masses, sometimes with lobulated features 1

Classification

Fibroadenomas can be classified as:

1. Simple: Most common type
2. Complex: Contains cysts >3 mm, epithelial calcifications, sclerosing adenosis, or papillary apocrine metaplasia
3. Giant: >5 cm in diameter or >500 grams
4. Juvenile/Myxoid: Occurs in adolescents 1, 2

Diagnosis and Management

Diagnostic Approach

The triple test is essential for accurate diagnosis:

1. Clinical examination
2. Imaging (ultrasound for younger women; ultrasound plus mammography for older women)
3. Tissue sampling (fine needle aspiration or core biopsy) 4

Management Options

For typical fibroadenomas with benign features confirmed by the triple test, observation is appropriate and surgical excision is not routinely necessary. 3

Indications for surgical intervention include:

• Diameter >2 cm
• Rapid growth
• Complex features on imaging
• Patient symptoms or anxiety
• Diagnostic uncertainty
• Need to exclude phyllodes tumor 1

Important Distinctions

• Phyllodes Tumor vs. Fibroadenoma:
  • Phyllodes tumors often appear similar to fibroadenomas on imaging
  • Clinical suspicion should be raised with:
    • Rapid growth
    • Large size (>2 cm)
    • History of growth 3
  • FNA and core biopsy may not reliably distinguish between them
  • Excisional biopsy may be needed for definitive diagnosis 3

Risk of Malignancy

The risk of malignancy in or adjacent to a fibroadenoma is very low (approximately 0.58% in core biopsied nodules) 5. The risk of cancer in a growing fibroadenoma is even rarer, with studies showing negligible incidence of malignant transformation 5.

Follow-up Recommendations

• Fibroadenomas without epithelial abnormalities diagnosed by core biopsy generally require no specific follow-up due to the negligible risk of malignant transformation 5
• For fibroadenomas managed conservatively, patients should be informed about the limitations of diagnostic tests and advised to seek prompt assessment if there are symptomatic or clinical changes 4

Common Pitfalls and Caveats

1. Diagnostic Uncertainty: A clinical diagnosis alone is unreliable and does not exclude malignancy, even in younger women 4

2. Distinguishing from Phyllodes Tumors: Large or rapidly growing fibroadenomas may be difficult to distinguish from phyllodes tumors, which require different management 3

3. Pregnancy-Associated Growth: Fibroadenomas may rapidly enlarge during pregnancy due to hormonal changes, sometimes requiring intervention to prevent permanent breast tissue damage 2

4. Complex Fibroadenomas: These require more careful evaluation as they may have slightly higher associated risk