Fibroadenoma

Most common breast mass in women <30 years. Estrogen-sensitive (grows in pregnancy, involutes in menopause).

Pathology variants

• Simple FA: Standard stromal/epithelial proliferation.
• Complex FA: Contains cysts >3mm, sclerosing adenosis, epithelial calcifications, or papillary apocrine metaplasia. slight $\uparrow$ risk of breast cancer (RR 1.5-2x).
• Giant FA: >5 cm or >500g.
• Juvenile FA: Rapid growth in adolescents.

Imaging findings

• Mammography:
  • Oval/round, circumscribed mass.
  • "Popcorn" calcifications: Pathognomonic for involuting FA (coarse, dystrophic).
• Ultrasound (US):
  • Oval, parallel orientation (wider-than-tall).
  • Circumscribed, macrolobulated.
  • Uniform hypoechogenicity.
• MRI:
  • Type 1 (persistent) or Type 2 (plateau) curve usually.
  • Dark Internal Septations: Non-enhancing septations on T1/T2 are highly specific (40-60%) for FA (vs Phyllodes).

Management

• Typical features (<2.5 cm): Observation.
• Growth: >20% increase in diameter in 6 months $\to$ Biopsy/Excision to rule out Phyllodes.
• Indication for removal: Symptomatic, rapid growth, >3 cm (often excised to avoid sampling error), or cosmetic deformity.