Fibroadenoma
Benign proliferation of breast lobular stroma + epithelium
Overview
The commonest benign breast tumour, typically in women under 35 — a smooth, firm, highly mobile, painless lump ('breast mouse'). Confirmed on triple assessment; most are left alone and many regress, with excision for large/growing/symptomatic lesions or patient choice.
Recognise
- Young woman (often <35); smooth, firm, well-defined, highly MOBILE, painless lump
- Usually <3 cm; may be multiple; oestrogen-sensitive (can grow in pregnancy)
- Benign — no skin/nipple change, no fixation
Red flags
- Rapidly growing/large (>3–4 cm) lesion → consider phyllodes tumour (excise)
- Atypia on biopsy / family history → individualised management
Differentials & how to tell them apart
Investigations
Triple assessment (age-appropriate): ultrasound (well-defined) ± mammography in older women; core biopsy if ≥25 or atypical.
Management
Reassurance/observation after triple assessment (excise if large/growing/symptomatic)
- 1Confirm benign nature on triple assessment. Reassure and observe small, typical fibroadenomas.Gate: Excise/biopsy if large (>3 cm), rapidly growing or atypical — to exclude a PHYLLODES tumour (which needs wide local excision)
- 2Excision for symptomatic/growing lesions or patient choice; routine follow-up not usually needed for small typical lesions.
Key points
Young woman + smooth, firm, very mobile painless lump = fibroadenoma ('breast mouse') → reassure after triple assessment. A rapidly enlarging fibroepithelial lump is phyllodes until excised.
Monitor & prognosis
Interval ultrasound if observed; growth.
Benign; often regresses.
Source: NICE NG101; CKS Breast