Adenomyoepithelioma of the Breast
Definition
- Biphasic epithelial/myoepithelial breast neoplasm with a clear expansion of the myoepithelial component
Diagnostic Criteria
- Biphasic with prominent myoepithelial component
- Tubules lined by cuboidal to columnar epithelial cells
- Frequent apocrine differentiation
- May be pushed to edge of nodule
- May be compressed, resembling multinucleated giant cells
- Prominent, expanded myoepithelial component
- Usually polygonal with clear cytoplasm
- May be spindled
- Range from evenly distributed to focal nests/nodules to predominant
- 95% of cases >25% myoepithelial
- 84% of cases >50% myoepithelial
- Positive staining for glycogen, keratin and muscle markers
- Usually polygonal with clear cytoplasm
- Both components cytologically bland
- Minimal pleomorphism
- Low mitotic rate
- Tubules lined by cuboidal to columnar epithelial cells
- Circumscribed lesion
- Lobulated, multinodular or papillary
- Pushing border but not infiltrating
- Occasional findings
- Basophilic background stroma
- Central necrosis and dystrophic calcification
- Focal fibromatosis-like myofibroblastic response
- May contain rare keratin positive cells
- No clinical significance
- In the literature, the term adenomyoepithelioma has been applied loosely to a variety of lesions
- If cytologically atypical or invasive, diagnose instead as appropriate type of carcinoma, sarcoma or malignant myoepithelial neoplasm
- Any other lesion present should be diagnosed separately as such
- Criteria above derived largely from McLaren 2005
- Identical in appearance to epithelial-myoepithelial carcinoma of salivary gland
Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting:: May 15, 2006