Fibroadenoma
Summary
Fibroadenoma is the most common benign breast tumour, composed of glandular and stromal tissue. It most commonly occurs in women aged 15-35 years. The classic presentation is a painless, smooth, well-circumscribed, highly mobile breast lump ("breast mouse"). Diagnosis is confirmed with triple assessment (clinical examination, ultrasound, and core biopsy). Fibroadenomas carry no malignant potential in most cases, though complex fibroadenomas may have slightly increased breast cancer risk. Most can be managed conservatively with reassurance. Surgical excision is offered for larger lesions (>3cm), rapid growth, patient preference, or diagnostic uncertainty.
Key Facts
- Peak Age: 15-35 years (reproductive years)
- Composition: Glandular (epithelial) + Stromal (connective tissue)
- Clinical Sign: Smooth, firm, mobile, non-tender lump ("breast mouse")
- Diagnosis: Triple assessment (Clinical + Ultrasound + Core biopsy)
- Malignancy Risk: Essentially none (simple fibroadenoma)
- Management: Conservative if <3cm; Excision if >3cm or growing
Clinical Pearls
"Breast Mouse": The classic fibroadenoma is so mobile it seems to slip away during palpation - hence the nickname.
"Simple ≠ Malignant": Simple fibroadenomas have NO increased cancer risk. Complex fibroadenomas (with cysts, apocrine metaplasia, sclerosing adenosis) may have marginally increased risk.
"Age Matters": In women >35, any new breast lump should undergo full triple assessment. Don't assume benign.
"Phyllodes if Growing Fast": Rapid growth, especially in older women, should raise concern for Phyllodes tumour (can be benign, borderline, or malignant).
Incidence
- Most common benign breast tumour
- Accounts for ~50% of breast biopsies in women <30
Demographics
- Peak age: 15-35 years
- Rare post-menopause (unless on HRT)
- Multiple in 15-20% of cases
- Bilateral in 10-15%
Risk Factors
- Young age (reproductive years)
- Black ethnicity (higher incidence)
- Oral contraceptive use (controversial)
- Higher oestrogen states
Natural History
- May regress spontaneously (especially post-menopause)
- Most remain stable or grow slowly
- Malignant transformation is exceptionally rare (<0.1%)
Histogenesis
- Arises from terminal duct lobular unit (TDLU)
- Consists of both glandular (epithelial) and stromal components
- Hormone-sensitive (oestrogen)
Types
| Type | Description |
|---|---|
| Simple | Single, well-encapsulated, no atypical features |
| Complex | Contains cysts, sclerosing adenosis, epithelial calcifications, apocrine metaplasia |
| Juvenile (Giant) | >cm, typically in adolescents, rapid growth |
| Phyllodes tumour | Related but distinct; can be benign, borderline, or malignant |
Hormonal Influence
- Oestrogen-responsive (grow in pregnancy, shrink post-menopause)
- May enlarge with HRT, OCP
- Lactational changes can occur
Symptoms
| Feature | Description |
|---|---|
| Lump | Usually painless; may notice incidentally |
| Size | Typically 1-3cm at presentation |
| Number | Single (80%); Multiple (20%) |
| Pain | Rarely; some have cyclical tenderness |
Characteristic Features ("Breast Mouse")
Signs Suggesting Malignancy (NOT Fibroadenoma)
Inspection
- Usually no visible abnormality
- Large fibroadenomas may cause asymmetry
Palpation
- Smooth, well-defined lump
- Firm, rubbery texture
- Highly mobile (moves freely within breast tissue)
- Non-tender
- May be difficult to feel if small or deep
Examination Technique
- Examine with patient supine
- Arms behind head to flatten breast tissue
- Palpate all four quadrants systematically
- Check axillary and supraclavicular nodes
Triple Assessment
- Clinical Examination (as above)
- Imaging:
- Ultrasound (first-line in <40 years)
- Well-circumscribed
- Homogeneous hypoechoic
- Oval/round shape
- Parallel orientation
- Mammography (≥40 years or if indicated)
- Well-defined dense mass
- Ultrasound (first-line in <40 years)
- Pathology:
- Core needle biopsy (B2 = benign)
- FNA less reliable (false negatives)
Ultrasound Features
| Benign (Fibroadenoma) | Concerning |
|---|---|
| Well-circumscribed | Irregular margins |
| Oval/lobulated | Spiculated |
| Parallel orientation | Non-parallel (taller than wide) |
| Homogeneous | Heterogeneous with calcifications |
| Posterior enhancement | Posterior shadowing |
When is Biopsy Essential?
- Any lump in woman >35
- Size >2-3cm
- Atypical imaging features
- Rapid growth
- Patient anxiety
Conservative Management (First-Line)
┌──────────────────────────────────────────────────────────┐
│ CONSERVATIVE MANAGEMENT │
├──────────────────────────────────────────────────────────┤
│ │
│ CRITERIA: │
│ • Size <3cm │
│ • Characteristic triple assessment findings │
│ • B2 (benign) on core biopsy │
│ • Not enlarging │
│ │
│ MANAGEMENT: │
│ • Reassurance │
│ • Single follow-up ultrasound at 12 months (optional) │
│ • Patient education on symptoms for review │
│ • Discharge if stable │
│ │
└──────────────────────────────────────────────────────────┘
Indications for Excision
| Indication | Rationale |
|---|---|
| Size >cm | Unlikely to regress; cosmetic |
| Rapid growth | Exclude Phyllodes |
| Patient preference | Anxiety |
| Diagnostic uncertainty | Exclude malignancy |
| Giant fibroadenoma (>cm) | Can cause significant asymmetry |
| Complex fibroadenoma | Marginally higher cancer risk |
Surgical Options
- Wide local excision: Standard open approach
- Vacuum-assisted excision: Minimally invasive, cosmetically preferred for smaller lesions
Alternative: Cryoablation
- Emerging technique using cryotherapy
- Suitable for small, confirmed fibroadenomas
- Cosmetically superior
Of Fibroadenoma
- Cosmetic concern (large lesions)
- Anxiety
- Rarely, misdiagnosis of malignancy
Of Surgery
- Scarring
- Haematoma
- Infection
- Seroma
- Recurrence (rare)
Natural History
- Many regress spontaneously
- Most remain stable
- Malignant transformation exceptionally rare (<0.1%)
Long-Term
- Simple fibroadenoma: NO increased breast cancer risk
- Complex fibroadenoma: 1.5-2x increased risk (still low absolute risk)
Recurrence
- Excision is curative for that lesion
- New fibroadenomas may develop (especially if young)
Key Guidelines
- Association of Breast Surgery (ABS) Guidelines
- NICE Referral Guidelines for Suspected Cancer (NG12)
- British Society of Breast Radiology (BSBR)
Key Evidence
Natural History
- Studies show 25-30% of fibroadenomas regress spontaneously
- Most remain stable over 2-year follow-up
Cancer Risk
- Dupont & Page (NEJM 1994): Complex fibroadenoma associated with 1.5-2x increased risk
- Simple fibroadenoma: No increased risk
Vacuum-Assisted Excision
- RCTs show similar outcomes to surgical excision with better cosmesis
What is a Fibroadenoma?
A fibroadenoma is a very common, non-cancerous (benign) breast lump. It's made up of normal breast tissue and connective tissue. It's often called a "breast mouse" because it moves easily under your fingers.
Who Gets Them?
Fibroadenomas are most common in young women (teens to early 30s). They can occur at any age but are rare after menopause unless you're taking HRT.
What Does it Feel Like?
- A smooth, round lump
- Firm but rubbery
- Moves freely when touched
- Usually painless
Is it Cancer?
No. Fibroadenomas are NOT cancer and do not turn into cancer. However, any new breast lump should be checked by a doctor to confirm the diagnosis.
How is it Diagnosed?
Your doctor will use three investigations ("triple assessment"):
- Examination of the breast
- Ultrasound scan
- Biopsy (taking a small sample to check under the microscope)
How is it Treated?
If it's small (<3cm) and confirmed to be a fibroadenoma, it usually doesn't need treatment - just reassurance. Surgery to remove it may be offered if:
- It's large (>3cm)
- It's growing
- It's causing you concern or discomfort
Do I Need Follow-Up?
Usually just one follow-up scan to check it's stable. If it's not changing, you can be discharged with advice to return if you notice any changes.
Primary Guidelines
- Association of Breast Surgery. Best Practice Diagnostic Guidelines for Patients Presenting with Breast Symptoms. 2016.
- NICE. Suspected cancer: recognition and referral (NG12). 2021 update.
Key Studies
- Dupont WD, Page DL. Risk factors for breast cancer in women with proliferative breast disease. N Engl J Med. 1985;312(3):146-151. PMID: 3965932
- Wechselberger G, et al. Long-term results of vacuum-assisted biopsy for treatment of benign breast lesions. Br J Surg. 2014.