Fibroadenoma

Section: Breast Curriculum: Curriculum, page 9

Definition

• Benign breast mass (not tumour as does not arise from single cell!)
• Develop from entire lobule
  • Both glandular (epithelial) and stromal (connective tissue) components from periductal intralobular fibroblasts
• “Benign fibro-epithelial lesion which originates from both the glandular and stromal components of the breast”

Incidence

• 10% females
• Most common in 21-25 yo - 60% of breast lumps in 20 yr olds
• Incidence decreases after menopause (< 5% occur in women > 50yrs)
• Except HRT
• Account for 1/3 - ½ of breast biopsies for benign disease
• Second most common mass in breast after carcinoma

Classification

• Simple
• Complex
  • Calcifications, cysts > 3mm, mixed histological features
• Giant fibroadenoma = > 5cm
• Juvenile – tends to be more cellular (~ puberty)

Aetiology

• Unknown (? ↑ Sensitivity to oestrogen → hyperplasia; ? a continuum of ANDI changes)
• Linked to OCP
• Cyclosporin → Multiple Fibroadenomas
• EBV
• Clinical
  • 80% are single
  • Hormonally responsive
  • Very mobile “breast mouse”
    • Origin is from lobular stroma – thus, not tethered to ducts – thus, mobile
  • Usually 1-3cm lump
  • Non-tender
  • Predominate in upper outer quadrant

Pathology

• Part of ANDI complex
• Well circumscribed nodule, pseudoencapsulated
• Proliferation of normal breast elements:
  • Intralobular stroma
    • Myxoid change, hyaline change
    • Stroma often distorts and compresses epithelial components
  • Epithelium (± Epithelial hyperplasia ± apocrine metaplasia)
• “Intracanalicular” & “Pericanalicular” patterns
  • Pericanalicular: fibrous tissue surrounding a few small tubular glands; tend to be small & hard
  • Intracanalicular: contain more glands, which are indented by fibrous tissue and stretched into elongated, spidery shapes; usually larger & softer
• Low cellularity
• Low mitotic rate
• ‘Complex fibroadenoma’
  • ↑ Cellularity, apocrine metaplasia, epithelial hyperplasia
• Differential Diagnosis:
  • Cyst, Phyllodes (esp. if > 3cm), Cancer, Hamartoma, Tubular adenoma (entire lesion consisting of glands with very little intervening stroma)

Investigations

• Mass = Triple assessment
• USS
  • Well circumscribed
  • Wider than it is long
  • Not traversing tissue planes
  • Homogeneous, (complex fibroadenoma may be heterogenous)
• Mammogram if > 35yrs
  • Smooth, density ≥ Surrounding breast (DDx = Cyst, but tend to be perfectly round)
  • +/- Stippled calcification with ↑ age
  • Popcorn appearance – lobulated appearance
  • Classically, fibroadenomas revealed on 1st mammogram
• Core biopsy preferred
  • May not need it in a small FA in women < 25 with classical features on imaging

Age of diagnosis: normal breast development stops at around age 25 Thus, if a truly new breast lesion develops after age 25, biopsy is required because it is bizarre for a new fibroadenoma to develop AFTER breast development has completed

Management

• Excise if > 3cm, growing, pt choice, strong FHx, can’t get FNA/core
• 90% of women elect to have them removed
• Surgical treatment = Enucleation
  • Same for simple or complex
  • NB: One does not need to close the space left behind after removing a fibroadenoma – as the lesion grows, it displaces the adjacent normal breast tissue away. Thus, after removal, the adjacent breast tissue springs back and fills the gap.
• Natural Hx:
  • Growth phase, can double in size every 6-12 months
  • Show hormonal dependence
  • Lactational changes & involution in menopause
  • Usually growth ceases at ≈ 2cm in size
  • 30% disappear, 50% stay the same, 10% increase, 10% shrink
  • Risk of developing Cancer is small (and Lobular more common than Ductal)
    • Simple fibroadenoma NO increased risk
  • Complex fibroadenoma: RR = 3.5
    • Unclear if they can progress to Phyllodes tumour
• Follow-up
  • For conservatively treated fibroadenoma, can R/V in 3-6/1

Northshore Hospital flow diagram

• Age

  • 35 → USS + Mammogram

  • <35 → USS
• All get Core biopsy
• Management
  • <1cm
    • Follow up scan in 6 months, if no change discharge
  • <3cm → excise if patient patient desires or family history

  • 3cm → offer excision