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Surgical Pathology Criteria

Lactating Adenoma of the Breast


  • A benign breast lesion composed of a circumscribed mass of densely packed regular round tubules with prominent secretory change

Diagnostic Criteria

  • Circumscribed mass
    • Sharply demarcated but no true capsule
  • Densely packed, uniform, round tubules
    • Two cell layers throughout
      • Lumenal cells epithelial
      • Ablumenal cells myoepithelial
    • Mitotic figures may be frequent
    • No cytologic atypia
  • Secretory change prominent
    • Cytoplasmic vacuoles
    • Lumenal eosinophilic secretion
    • Secretory changes may be less prominent if resected prepartum
  • Scant stroma
    • No compression of ducts
  • Tubular adenoma may represent the same lesion under different physiologic conditions
    • Tubular adenoma has been identified in postpartum biopsies of masses that first presented during pregnancy

Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting:: May 15, 2006

Supplemental studies


  • Ablumenal cells positive for myoepithelial markers
    • Calponin, p63, smooth muscle actin positive
    • S100 positive

Fat Stains

  • Cytoplasmic vacuoles and lumenal secretion positive

Differential Diagnosis

Lactating Adenoma Tubular Adenoma
Prominent lactational change Lumenal secretion may be present, but cytoplasmic vacuoles lacking
These may represent the same lesion under different physiologic conditions


Lactating Adenoma Focal Pregnancy-like Change
Circumscribed mass Focal change in breast parenchyma


Lactating Adenoma Secretory Carcinoma
Circumscribed mass of uniform round tubules Sheet-like growth with focal infiltration
Myoepithelial cells present No myoepithelial cells


  • Most cases occur between 19-34 years of age
  • Rare lesion
  • Patients pregnant or lactating
  • No recurrences reported
  • No evidence for increased risk of carcinoma
  • May occur in ectopic locations


Breast Adenomas (not all are true adenomas)


  • O'Hara MF, Page DL. Adenomas of the breast and ectopic breast under lactational influences. Hum Pathol. 1985 Jul;16(7):707-12.
  • Hertel BF, Zaloudek C, Kempson RL. Breast adenomas. Cancer. 1976 Jun;37(6):2891-905.
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