General
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• Uncommon variant of adenosis with proliferation of epithelial and myoepithelial cells

Terminology
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• Also called apocrine adenosis or secretory adenosis (Stanford School of Medicine), although adenomyoepithelial adenosis has prominent myoepithelial cells in 1-3 layers

Clinical features
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• Present with a palpable mass 1.3-5.5 cm
• May be a precursor to benign adenomyoepithelioma (Am J Clin Pathol 1988;89:308, Virchows Arch A Pathol Anat Histopathol 1984;405:55), malignant adenomyoepithelioma (Virchows Arch A Pathol Anat Histopathol 1984;405:55) or invasive duct carcinoma (Springerplus 2013;2:50)

Radiology
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• No specific features
• May show focal asymmetry, irregular margins or microcalcification and mimic malignancy

Case reports
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• 35 year old woman with adenomyoepithelial adenosis associated with breast cancer (Springerplus 2013;2:50)
• 46 year old woman (Breast Care (Basel) 2008;3:427)
• Malignant progression of adenomyoepithelial adenosis of breast (Pathol Int 1994;44:475)

Treatment
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• Excision recommended due to possibility of recurrence and association with malignancy
• Best predictors of recurrence are initial incomplete excision and close margins

Clinical images
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Left breast

Hypoechoic mass

Irregular spiculated dense mass

Spiculated hypoechoic mass

Micro description
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• 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

Micro images
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Adenomyoepithelial adenosis

Myoepithelial cells

AE1/AE3

SMA+

Positive stains
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• Myoepithelial cells are positive for p63, CK 5/6, S100, αSMA

Differential diagnosis
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• Cannot be distinguished from a microscopic adenomyoepithelioma

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