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Surgical Pathology Criteria

Microglandular Adenosis of the Breast


  • A haphazard proliferation of uniform, cytologically bland glands

Diagnostic Criteria

  • Small, uniform open round glands
    • Lined by uniform cuboidal to slightly flat cells
    • Nuclei frequently flattened, parallel to circumference of gland
    • Clear to eosinophilic cytoplasm
    • Lumenal eosinophilic colloid-like secretion
      • Occasional luminal calcification
  • Cytologically bland
    • Small indististinct nucleoli
    • Mitotic figures uncommon
  • Haphazard distribution
    • Poorly circumscribed
    • No lobular grouping
    • Not stellate
    • Frequently overruns normal elements
    • No perineural or vascular invasion
  • Background of fibrous or fatty tissue
    • No spindle cell or desmoplastic component
  • No myoepithelial layer
  • Carcinoma, in situ and invasive, has been reported in association with microglandular adenosis
    • Reported in up to 27%
    • Apparently disproportionate numbers of metaplastic, adenoid cystic and basal-like carcinomas
    • Transitional atypical microglandular adenosis has been proposed
      • Increased irregularity and density of glands
      • Increased cytologic atypia
        • Hyperchromasia, prominent nucleoli, apoptosis
      • Increased Ki67 and p53 staining (5-10% of cells)
    • Carcinomas retain the immunophenotype of microglandular adenosis

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
Updates: January 20, 2009

Supplemental studies


S100 100% diffuse
CK8/18 100%
EGFR 100%
EMA Negative
GCDFP15 Negative
CK5/6 Negative
Smooth muscle actin Negative
ER, PR Negative
Her2neu Negative
CD117 Negative
Collagen type IV Positive basement membrane
Ki67 <3%
p53 <3%
CD117 may be positive in associated CIS or carcinoma
  • Ki67 and p53: 5-10% in microglandular adenosis with atypia, >30% in carcinoma


  • Lumenal secretion positive for PASd and other mucin stains

Differential Diagnosis

Tubular Carcinoma Microglandular Adenosis
Stellate, infiltrating Nodular or diffuse
Round to oval ducts with pointed ends and gaping lumens Uniform small round ducts with small lumens
Frequent apical snouts No apical snouts
Empty lumens Eosinophilic secretion present in at least some lumens
Larger cells, polarized to lumen Cells smaller, flatter
Round nuclei Nuclei may be flat, parallel to base
EMA positive EMA negative
Basement membrane absent Basement membrane variable
Both have rounded non-branching ducts with a single layer of cells, lacking myoepithelial cells


Sclerosing Adenosis Microglandular Adenosis
Prominent myoepithelial cells No myoepithelial cells
Cellular, sclerotic stroma Stroma collagenous or adipose
Lobular Haphazard
Compressed lumens Uniform round glands


Apocrine Adenosis Microglandular Adenosis
Myoepithelial layer present, may be hyperplastic No myoepithelial cells
Variable size and shape of glands Uniform round glands
Apocrine lumenal differentiation and in some cases squamous metaplasia present No squamous or apocrine metaplasia
EMA and GCDFP15 positive EMA and GCDFP15 negative


Microglandular Adenosis Tubular Adenosis
Uniformly round lumens Predominantly tubular
Cytoplasm frequently clear Cytoplasm eosinophilic
No myoepithelial layer Myoepithelial cells present
Secretion eosinophilic Secretion eosinophilic or basophilic


Microglandular Adenosis Tubular Adenoma
Poorly circumscribed pattern Circumscribed
Surrounds normal elements Mass displaces normal elements
No myoepithelial cell layer Myoepithelial cell layer present
Haphazardly scattered tubules Densely packed tubules
Abundant fibrous or fatty stroma Scant stroma


  • Age range 28-82 years
    • Mean about 50 years
  • May be a palpable mass or an incidental finding
  • No metastases reported
  • May recur
    • Very rare aggressive local recurrence
  • Carcinoma may be associated with microglandular adenosis
    • Conservation of immunophenotype and apparent transitional atypical cases support the possibility that microglandular adenosis is a precursor of carcinoma
    • Incidence is unknown but reported as high as 27%
    • Suggests that complete resection is indicated


Adenosis of the Breast


  • Clement PB, Azzopardi JG. Microglandular adenosis of the breast--a lesion simulating tubular carcinoma. Histopathology. 1983 Mar;7(2):169-80.
  • Tavassoli FA, Norris HJ. Microglandular adenosis of the breast. A clinicopathologic study of 11 cases with ultrastructural observations. Am J Surg Pathol. 1983 Dec;7(8):731-7.
  • Eusebi V, Foschini MP, Betts CM, Gherardi G, Millis RR, Bussolati G, Azzopardi JG. Microglandular adenosis, apocrine adenosis, and tubular carcinoma of the breast. An immunohistochemical comparison. Am J Surg Pathol. 1993 Feb;17(2):99-109.
  • Tavassoli FA, Bratthauer GL. Immunohistochemical profile and differential diagnosis of microglandular adenosis. Mod Pathol. 1993 May;6(3):318-22.
  • Diaz NM, McDivitt RW, Wick MR. Microglandular adenosis of the breast. An immunohistochemical comparison with tubular carcinoma. Arch Pathol Lab Med. 1991 Jun;115(6):578-82.
  • Rosen PP. Microglandular adenosis. A benign lesion simulating invasive mammary carcinoma. Am J Surg Pathol. 1983 Mar;7(2):137-44
  • Khalifeh IM, Albarracin C, Diaz LK, Symmans FW, Edgerton ME, Hwang RF, Sneige N. Clinical, histopathologic, and immunohistochemical features of microglandular adenosis and transition into in situ and invasive carcinoma. Am J Surg Pathol. 2008 Apr;32(4):544-52.
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