Surgical Pathology Criteria

Adenomyoepithelioma of the Breast

Differential Diagnosis

 

Various processes may have prominent atypical myoepithelial cells

 

Adenomyoepithelioma Myoid Hamartoma
Myoepithelial component positive for keratin, p63, smooth muscle actin Myoid component positive only for smooth muscle actin
Tubules without lobules Well formed ducts and lobules
No admixed fat Admixed fat

 

Pleomorphic Adenoma Adenomyoepithelioma
Chondromyxoid stroma Lacks chondromyxoid stroma
Otherwise the lesions may be identical

 

Low Grade Adenosquamous Carcinoma Adenomyoepithelioma
Squamous differentiation frequent Squamous differentiation not described
Infiltrative pattern Circumscribed, not infiltrative
Otherwise the lesions may be identical

 

Papilloma with Prominent Myoepithelial Cells Adenomyoepithelioma
Myoepithelial cells restricted to basal layer on papillae Prominent, expanded myoepithelial component forming nodules or nests

 

Ductal Adenoma Adenomyoepithelioma
Hyalinized stroma Cellular stroma
Circumscribed, encapsulated Capsule unusual
Ductal adenoma may have myoepithelial overgrowth

 

Metaplastic Carcinoma Adenomyoepithelioma
Glandular component, if present, is histologically malignant, except in low grade spindle cell metaplastic carcinoma Epithelial component is histologically bland
Stromal component may be bland or histologically malignant Stroma is histologically bland
Stromal component may resemble a variety of sarcomas or low grade fibrous proliferation Stroma shows myoepithelial differentiation only
Squamous differentiation may be present No squamous differentiation

 

Myofibroblastoma Adenomyoepithelioma
No epithelial component Tubules integral to lesion
Stromal keratin negative, CD34 positive, muscle/myoid markers variable Stromal keratin variable, p63 and muscle/myoid markers positive

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