Breast - nonmalignant
Benign (usually) tumors / tumor like-changes
Adenomyoepithelioma

Author: Monika Roychowdhury, M.D., FCAP (see Authors page)

Revised: 2 June 2016, last major update June 2016

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Adenomyoepithelioma [title] breast
Cite this page: Adenomyoepithelioma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/breastadenomyo.html. Accessed December 10th, 2016.
Definition / General
  • Biphasic tumor composed of variable number of myoepithelial cells around small epithelial lined spaces
  • First recognized in the breast by Hamperl (Curr Top Pathol 1970;53:161)
Essential Features
  • Biphasic tumor with epithelial and myoepithelial components
  • Benign to low grade malignant behavior and a propensity for recurrence
  • Either epithelial or myoepithelial component can show malignant transformation so thorough evaluation recommended
  • Wide surgical excision with appropriate margins recommended to prevent recurrence
  • Microscopy shows tubular or lobular structures with epithelial and myoepithelial components
  • IHC: Epithelial component is cytokeratin+, EMA+, CEA+; myoepithelial component is S100+, SMA+, SMM-HC+, p63+
Terminology
  • Other breast myoepithelial lesions are myoepitheliosis and myoepithelioma
  • WHO (2012) divides adnomyoepithelioma into a benign type (both components benign) and a form where malignant transformation is seen
  • Page recommends that cases with malignant histology not be called adenomyoepithelioma but be defined by the histology of the malignant component (Am J Surg Pathol 2005;29:1294)
Epidemiology
  • Uncommon, mean age 60 years
  • Rare in male breast
Sites
  • Usually occurs in the peripheral portion of the breast, but can be central
  • No predilection for either breast
Etiology
  • Considered a variant of intraductal papilloma
Clinical Features
  • Usually presents as a mass
  • Usually benign, although may recur locally
  • Benign appearing tumors rarely metastasize to lung (Arch Pathol Lab Med 2006;130:1349)
  • Malignant tumors are usually low grade; may metastasize to lung, brain, jaws, lymph nodes
  • If metastasize, shows hematogenous spread, usually occurs in tumors > 1.6 cm in size (World J Surg Oncol 2013;11:285)
Prognostic Factors
  • Mitotic rate > 3 MF / 10 HPF is associated with recurrence
  • Tubular variant and some lobular variants with high mitotic activity are prone to recurrence
  • High mitotic rate, atypia, necrosis, cellular pleomorphism and infiltrative borders favor malignancy
Case Reports
Malignant tumors
Treatment
  • Wide local excision with appropriate margins
  • May recur with incomplete excision
Clinical Images

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Mammogram - courtesy of Dr. Mark R. Wick



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Radiological characteristics of lesion

69 year old woman (fig 1A, 1B)

Gross Description
  • Well circumscribed, usually small (mean 1 - 2 cm), but can be up to 8 cm
  • Firm
  • May have satellite nodules
Gross Images

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Unusually large bisected tumor with central
cavity with bosselated contour (AFIP)



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Intracystic nodule

Micro Description
  • Well circumscribed, may be encapsulated or multinodular
  • Proliferation of epithelial and myoepithelial cells
  • Aggregated lobules of glands with tall lining epithelium with scant eosinophilic cytoplasm and hyperchromatic nuclei surrounded by myoepithelial cells with clear cytoplasm
  • Epithelial cells usually form glandular spaces
  • Myoepithelial cells can be dominant and may be spindle shaped, clear or polygonal
  • Apocrine metaplasia may be present, also adenomyoepitheliomatous hyperplasia
  • Variants include spindle cell type (epithelial lined spaces may be sparse, resembles leiomyoma), tubular variant (ill defined margins, may resemble tubular adenoma), lobulated variant (nests of myoepithelial cells surround compressed epithelial lined spaces)
  • Malignant appearing cases have local invasion, high mitotic rate, severe atypia (Am J Surg Pathol 1992;16:868)
Micro Images

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Courtesy of Dr. Mark R. Wick



AFIP Images:

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Intraductal bands of pale myoepithelium separate adenomatous ductal epithelium

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Myoepithelial cells with clear cytoplasm crowd glandular epithelium and expand into stroma

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Overgrowth of myoepithelium in two nodules separated by stromal band

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Myoepithelial cells in small clusters have replaced most ductal elements

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Foci of glands with luminal secretions

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Isolated myoepithelial cells with clear vacuolated cytoplasm

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Transition between adenomatous and myomatous growth

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AE1+ glandular cells, (myoepothelial cells are negative)



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Proliferation of epithelial and myoepithelial cells



Multilobulated outlines and pushing margins

CK7 (A); p63 (B); CK5 (C); S-100 (D)

69 year old woman (fig 1C)

72 year old woman (fig 2C)

74 year old woman (fig 3C, 3D, 3E)

Solid sheets and cords of round, oval cells

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Various images and stains

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With collagenous spherulosis


Benign histology but malignant behavior:

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Benign appearing tumors that metastasized to lung

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Lung metastases with benign histology



Malignant histology:

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Mitotic activity

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Various images

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Keratin+ epithelium

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AE1-AE3, S100

Cytology Description
  • Moderate to highly cellular with large clusters of epithelium and myoepithelium
  • Tubular structures occasionally found
  • Myoepithelium appears as small clusters or dispersed cells with epithelioid morphology, intranuclear or intracytoplasmic vacuoles, often naked bipolar nuclei
  • Mild to moderate nuclear atypia present
  • Metachromatic fibrillary stroma occasionally found
  • No mitotic figures, no necrosis
  • Often classified incorrectly as fibroadenoma, suspicious for malignancy or malignant (Cancer 2006;108:250)
Cytology Images

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Various images

Positive Stains
Negative Stains
Electron Microscopy Description
  • Myoepithelial features (classic) include myofibrils with dense bodies, pinocytotic vesicles, desmosomes or tight junctions, patchy basement membrane
Molecular / Cytogenetics Description
Differential Diagnosis