Fibrocystic changes

Adenomyoepithelial adenosis

Editorial Board Member: Gary Tozbikian, M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Julie M. Jorns, M.D.

Last author update: 7 December 2020
Last staff update: 9 May 2022

Copyright: 2002-2023,, Inc.

PubMed Search: Adenomyoepithelial adenosis OR tubular variant of adenomyoepithelioma

Julie M. Jorns, M.D.
Page views in 2022: 6,739
Page views in 2023 to date: 7,564
Cite this page: Jorns JM. Adenomyoepithelial adenosis. website. Accessed November 29th, 2023.
Definition / general
  • Uncommon variant of adenosis with proliferation of epithelial and myoepithelial cells
Essential features
  • Lobulocentric proliferation of both epithelial and myoepithelial components
  • Prominent myoepithelial cells, 1 - 3 layers
ICD coding
  • ICD-10:
    • N60.2 - fibroadenosis of breast
  • ICD-11:
    • GB20.1 - fibroadenosis of breast
    • GB20.Y - other specified benign breast disease
  • Lobulocentric but otherwise no specific location within the breast
  • Unknown
  • Unknown
Clinical features
  • Histologic examination of tissue with or without immunohistochemistry
Radiology description
  • No specific features
  • May show asymmetry, architectural distortion or mass with irregular margins, with or without microcalcifications
Radiology images

Images hosted on other servers:

Left breast

Hypoechoic mass

Irregular spiculated dense mass

Spiculated hypoechoic mass

Prognostic factors
  • Unknown but progression to malignancy may be associated with older age (> 50 years) and mass on imaging (Springerplus 2013;2:50)
Case reports
  • Excision recommended due to possibility of recurrence and association with malignancy
  • Best predictors of recurrence are initial incomplete excision and close margins
Gross description
  • May form a firm mass with circumscribed or ill defined borders or may be grossly indistinguishable from surrounding fibrotic breast tissue
Microscopic (histologic) description
  • Multiple foci of haphazardly arranged ducts with eosinophilic granular secretions
  • Lined by cuboidal to columnar cells surrounded by hyperplastic myoepithelial cells
  • Resembles microglandular adenosis but with larger and more irregularly shaped glands, taller lining epithelial cells with eosinophilic granular cytoplasm and bland basal nuclei
  • May show apocrine or squamous metaplasia (Breast Care (Basel) 2008;3:427)
  • May have mild nuclear atypia
  • Rare to no mitotic activity
Microscopic (histologic) images

Contributed by Julie M. Jorns, M.D.
Adenomyoepithelial adenosis


Positive stains
Sample pathology report
  • Right breast, core biopsy:
    • Benign breast tissue with adenomyoepithelial adenosis
Differential diagnosis
Board review style question #1
Adenomyoepithelial adenosis Adenomyoepithelial adenosis

    The breast lesion pictured (H&E and p63 IHC, 20x) is most difficult to distinguish from which of the following lesions on core biopsy?

  1. Adenomyoepithelioma
  2. Invasive ductal carcinoma
  3. Microglandular adenosis
  4. Phyllodes tumor
Board review style answer #1
A. Adenomyoepithelioma. The pictured lesion is adenomyoepithelial adenosis, an uncommon variant of adenosis with a prominent myoepithelial component. This benign lesion may be difficult to distinguish from adenomyoepithelioma, which forms a circumscribed tumor but has similar microscopic features. Adenomyoepithelial adenosis, like other adenosis variants, may have similar features to microglandular adenosis or low grade invasive ductal carcinoma; however, these lesions lack myoepithelium, which is readily evident in adenomyoepithelial adenosis. Phyllodes tumor is a fibroepithelial neoplasm with dissimilar features, namely stromal proliferation with a resulting leaf-like growth pattern.

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Reference: Adenomyoepithelial adenosis
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