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Fibroadenoma of Breast USMLE Notes & Mnemonics contains all the high-yield points you need to know.


  • Fibroadenoma: Benign, solid, and well-circumscribed breast tumor composed of both stromal and glandular tissue.


  • Most common benign tumor of the breast.
  • Typically occurs in young women aged 15-35 years. (Ref)


  • Hormone Sensitive: Growth influenced by estrogen; may enlarge during pregnancy and involute with menopause.

Clinical Features:

  • Palpable Mass: Mobile, firm, rubbery, and painless; classically described as a “marble in the breast”.
  • Well-Delineated: Feels smooth and has clear edges.
  • No Associated Lymphadenopathy: Usually does not affect lymph nodes.


  • Physical Examination: Consistent with a movable, well-circumscribed mass.
  • Ultrasound: First-line imaging for women under 30 or pregnant (radiation-free).
  • Mammography: Typically shows a well-defined, round, or oval mass with smooth margins.
  • Fine-Needle Aspiration (FNA) or Core Biopsy: To confirm diagnosis if imaging is inconclusive.


  • Observation: Most do not require treatment; regular follow-up if asymptomatic and confirmed benign.
  • Surgical Excision: Indicated if there are concerns for cancer, rapid growth, or patient preference.

High-Yield Mnemonic: “FAB M&M” for Fibroadenoma Features

  • Firm
  • Age (young women)
  • Benign
  • Mobile
  • &
  • Marble-like

Chart: Differentiating Fibroadenoma from Cancer

FeatureFibroadenomaBreast Cancer
AgeYoung women (15-35 years)Older age group (post-menopausal)
ConsistencyFirm and rubberyHard, irregular
MobilityMobile (“breast mouse”)Fixed
BorderWell-circumscribedPoorly defined, irregular
GrowthSlow growingCan grow rapidly
PainUsually painlessMay be tender or painless
LymphadenopathyAbsentMay have associated lymphadenopathy
ImagingWell-defined, solid mass on ultrasoundSpiculated, irregular mass
BiopsyStroma and glandular elements without atypiaAtypical or malignant cells

Check other important USMLE Notes

Note: On USMLE, fibroadenomas are commonly presented as a young woman with a palpable, painless, and mobile breast lump. It is important to distinguish between a fibroadenoma and malignant lesions. The management of fibroadenoma is conservative unless symptoms are present or there is concern for malignancy. Remember, fibroadenomas are hormone-sensitive, so changes in size are often related to the menstrual cycle or pregnancy.

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