Fibroadenoma

Fibroadenoma is the commonest benign solid breast tumour of young women, composed of fibrous and glandular tissue. It arises from the terminal duct lobular unit and is hormone responsive.

• Peak age 15 to 35 years, though can occur at any age. About 10 percent of women develop one in their lifetime. Often multiple (15 to 20 percent) and bilateral.
• Variants: simple, complex (cysts, sclerosing adenosis, epithelial calcifications, papillary apocrine change; small increase in cancer risk), giant (over 5 cm), juvenile (adolescents, rapid growth).
• Natural history: about one third regress, one third remain unchanged, and one third grow, particularly in pregnancy, during oestrogen therapy or lactation; they involute and calcify after menopause.
• Malignant transformation is rare (under 0.3 percent, typically lobular carcinoma in situ within a fibroadenoma). Phyllodes tumour is the main differential (leaf like pattern, rapid growth, usually age 40 and over).
• Risk of breast cancer is slightly increased (relative risk about 1.5 to 2) for complex fibroadenomas and family history.

• A painless, firm, rubbery, smooth, well defined, highly mobile lump ("breast mouse"), 1 to 3 cm, round or oval, with a lobulated surface, often in the upper outer quadrant, not attached to skin, no axillary nodes, no nipple discharge.
• May be tender around menses in some. Does not change with the cycle.
• Red flags (suspect phyllodes tumour or cancer): rapid growth, size over 3 to 5 cm, age over 35 to 40 with a new lump, hard, irregular or fixed mass, skin stretching or ulceration, nipple retraction, axillary nodes, bloody discharge, recurrence after excision, family history of breast cancer, personal history of breast cancer, ill defined margins on imaging.

• Triple assessment (clinical examination, imaging, core biopsy) for every new breast lump.
  • Ultrasound (age under 40): oval, circumscribed, hypoechoic, wider than tall, with homogenous echotexture and posterior enhancement.
  • Mammography (age 40 and over): well defined round or oval mass, sometimes with coarse "popcorn" calcifications in older women.
  • Core needle biopsy (14 gauge, ultrasound guided) for histological confirmation; fine needle aspiration cannot reliably distinguish fibroadenoma from phyllodes.
• Women under 25 with a classic, small fibroadenoma on ultrasound can sometimes be managed on imaging alone with biopsy at the specialist's discretion.
• MRI is not needed routinely.

• Confirmed fibroadenoma under 3 cm in a young woman with concordant triple assessment: reassurance and conservative follow up (clinical review and repeat ultrasound at 6 and 12 months; discharge if stable); the risk of cancer is negligible.
• Excision (open excision or vacuum assisted excision under ultrasound, or cryoablation for small lesions) is considered for:
  • Size over 3 cm, or rapid growth.
  • Patient anxiety or preference.
  • Suspicion of phyllodes tumour or discordant biopsy.
  • Age over 35 to 40 with a new mass.
  • Complex fibroadenoma with atypia, giant or juvenile fibroadenoma.
  • Symptomatic lumps (pain, cosmetic distortion).
  • Lesions in women who are pregnant or planning pregnancy (large lesions).
• Surgery risks: bleeding, infection, scar, asymmetry; recurrence or new fibroadenomas appear in about 10 to 20 percent.
• Pregnancy: observe; most will enlarge; excise after pregnancy unless suspicious.
• Phyllodes tumours: wide local excision with 1 cm margins (borderline or malignant types may need mastectomy and oncology review).
• Teach breast awareness; screening mammography at age appropriate intervals; counsel that fibroadenoma does not require hormonal therapy.
• Follow up: 6 to 12 months; refer earlier for growth or change.