Epithelial-myoepithelial tumors


Editorial Board Member: Gary Tozbikian, M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Melissa Krystel-Whittemore, M.D.
Hannah Y. Wen, M.D., Ph.D.

Last author update: 11 January 2021
Last staff update: 9 May 2022

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PubMed Search: adenomyoepithelioma

Melissa Krystel-Whittemore, M.D.
Hannah Y. Wen, M.D., Ph.D.
Page views in 2022: 20,175
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Cite this page: Krystel-Whittemore M, Wen HY. Adenomyoepithelioma. website. Accessed November 29th, 2023.
Definition / general
  • Biphasic tumor composed of variable number of myoepithelial cells surrounding epithelial lined spaces
  • Usually expanded and prominent myoepithelial component
  • 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 lobulated structures with epithelial and myoepithelial components
  • Epithelial component: cytokeratin+, EMA+, CEA+; myoepithelial component: S100+, SMA+, SMMHC+, p63+
  • WHO (2019) divides adenomyoepithelioma into benign and malignant tumors
  • Malignant adenomyoepithelioma = adenomyoepithelioma with carcinoma, which can arise in epithelial or myoepithelial component or in both components (J Clin Pathol 2013;66:465)
ICD coding
  • Adenomyoepithelioma
    • ICD-O: 8983/0 adenomyoepithelioma
    • ICD-11: 2F30.Y & XH2V57 - other specified benign neoplasm of breast and adenomyoepithelioma, benign
  • Malignant adenomyoepitheliomas
    • ICD-O: 8562/3 epithelial-myoepithelial carcinoma
    • ICD-11: 2C6Y & XH7TL5 - malignant neoplasms of breast and adenomyoepithelioma with carcinoma
Clinical features
  • Well circumscribed mass, infrequently associated with tenderness and nipple discharge
  • Diagnosis on core biopsy specimen can be challenging
    • Presence of tightly aggregated glands arranged in compact nodules and prominent clear cell or spindle cell myoepithelium are clues to the diagnosis (Breast J 2004;10:522)
    • Immunohistochemical stains for myoepithelial markers are useful to highlight the myoepithelial component (Breast J 2004;10:522)
    • Excision is necessary for thorough evaluation of atypia or carcinoma arising in an adenomyoepithelioma
Radiology description
Radiology images

Contributed by Melissa Krystel-Whittemore, M.D. and Mark R. Wick, M.D.
Mammogram, irregular mass

Mammogram, irregular mass

Ultrasound, hypoechoic mass

Ultrasound, hypoechoic mass



Prognostic factors
  • Tubular type of adenomyoepithelioma, intraductal extension along periphery of lesion, incomplete excision and cytologic atypia are associated with local recurrence (Am J Surg Pathol 1991;15:554)
  • High mitotic rate, atypia, necrosis, cellular pleomorphism and infiltrative borders favor malignancy (Am J Surg Pathol 1992;16:868)
  • Malignant adenomyoepithelioma has prognosis dependent on histological subtype and grade of the malignant component
Case reports
  • Complete wide excision with negative margins is standard treatment to prevent local recurrence
  • Mastectomy with or without axillary node dissection - only needed if malignant transformation
  • Reference: AJR Am J Roentgenol 2003;180:799
Gross description
  • Usually solitary nodule, median size: 2 cm, can be up to 8 cm (Breast J 2020;26:653)
    • Recurrent tumors usually larger
  • Sectioning reveals well circumscribed, firm, pink-white to gray-tan lesion
  • Can have focal cystic changes or necrosis
  • Malignant adenomyoepithelioma can show infiltrative borders (J Clin Pathol 2011;64:477)
Gross images

Contributed by Melissa Krystel-Whittemore, M.D., Case #418
Tan-gray mass

Tan-gray mass

Malignant adenomyoepithelioma Malignant adenomyoepithelioma

Malignant adenomyoepithelioma

Microscopic (histologic) description
  • Well circumscribed, may be encapsulated or multinodular and lobulated
  • Biphasic proliferation of epithelial and myoepithelial cells
  • Epithelial cells usually form glandular spaces; can show apocrine, sebaceous or squamous metaplasia
    • Can have papillary epithelial proliferation
  • Myoepithelial cells usually dominant and may be polygonal shaped with clear cytoplasm or spindled
  • Variants:
    • Spindle cell: spindle myoepithelial cells proliferation, epithelial lined spaces may be sparse
    • Tubular: proliferation of rounded tubules, ill defined margins
    • Lobulated: nests of myoepithelial cells surround compressed epithelial lined spaces
  • Malignant cases have infiltrative growth pattern, high mitotic rate or severe atypia which can be seen in the epithelial or myoepithelial component or in both components (Arch Pathol Lab Med 2000;124:632, Am J Surg Pathol 1992;16:868, Virchows Arch 1998;432:123)
  • Malignant transformation of epithelial component can have features of invasive carcinoma no special type, invasive lobular carcinoma, metaplastic carcinoma, including squamous cell carcinoma, spindle cell carcinoma or matrix producing carcinoma, low grade adenosquamous carcinoma or adenoid cystic carcinoma (Breast 2016;29:132, Pathol Int 2009;59:179, Virchows Arch 1995;427:243, Pathol Res Pract 2007;203:599, Virchows Arch 1998;432:123, Am J Surg Pathol 1998;22:631, Breast J 2019;25:731, Diagn Pathol 2014;9:148)
  • Malignant transformation of myoepithelial component shows features of myoepithelial carcinoma including overgrowth of myoepithelial cells, nuclear atypia and mitotic activity (Pathol Int 2006;56:211, Breast J 2007;13:203, J Clin Pathol 2011;64:477)
  • Biphasic malignant tumors (of epithelial and myoepithelial components) can be seen, with myoepithelial cells being the predominant component (Breast J 2019;25:1273)
    • Usually multilobulated or multinodular and can show a distinct transition from benign to malignant components
    • Malignant changes must be seen in both epithelial and myoepithelial cell types, specifically including increased mitotic activity
  • Malignant adenomyoepithelioma can be ER positive or negative but the carcinoma component is most commonly ER / PR / HER2 negative (Nat Commun 2018;9:1816)
Microscopic (histologic) images

Contributed by Hannah Y. Wen, M.D., Ph.D.

Circumscribed lobulated tumor

Myoepithelial cells surrounding glands

Compressed tubules

Hyaline-like basement membrane



Contributed by Fresia Pareja, M.D., Ph.D.
Biphasic epithelial and myoepithelial proliferation

Malignant adenomyo-

Biphasic epithelial and myoepithelial proliferation

Biphasic epithelial and myoepithelial proliferation

Biphasic epithelial and myoepithelial proliferation with nuclear atypia and mitoses

Nuclear atypia and mitoses

Biphasic epithelial and myoepithelial proliferation with fat invasion

Fat invasion

Virtual slides

Images hosted on other servers:


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)
  • Malignant adenomyoepithelioma is highly cellular with neoplastic appearing cells
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
Molecular / cytogenetics images

Images hosted on other servers:
<i>MYC</i> amplification

MYC amplification

Sample pathology report
  • Breast, left, excision:
    • Adenomyoepithelioma, 3.2 cm
    • Surgical margins negative for tumor
Differential diagnosis
  • Sclerosing adenosis:
    • Proliferation of epithelial glands with stromal sclerosis, which can cause architectural distortion of the glands
    • Less commonly mass forming
    • No prominent myoepithelial component
  • Intraductal papilloma:
    • Papillary lesion comprised of epithelial proliferation with fibrovascular cores
    • No prominent myoepithelial component
  • Invasive carcinoma (on core biopsy):
    • Malignant epithelial proliferation
    • Unequivocal evidence of invasion
    • Negative for myoepithelial markers (p63 / p40, SMMHC, calponin, CK5)
  • Nipple adenoma:
    • Epithelial proliferation arising in the collecting ducts of the nipple
    • No prominent myoepithelial component
  • Tubular adenoma:
    • Very well circumscribed
    • Proliferation of tubules with only single layer of myoepithelial cells surrounding the epithelial component without expansion of myoepithelial component
Board review style question #1

A 58 year old woman presents with a 2 cm nontender, firm nodule in the upper outer quadrant of her left breast. A core biopsy and subsequent resection of the lesion is performed. Representative microscopic images from the excision specimen are shown, which revealed an adenomyoepithelioma. Which of the following is true?

  1. Chemotherapy is the standard treatment of this lesion
  2. This lesion is usually HER2 positive and treated with anti-HER2 therapy
  3. This is a malignant lesion
  4. Without negative surgical margins, there is a risk of local recurrence of the lesion
Board review style answer #1
D. Without negative surgical margins, there is a risk of local recurrence of the lesion

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Reference: Adenomyoepithelioma
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