Pleomorphic Adenoma of the Breast

Definition

Rare breast neoplasm with epithelial, myoepithelial and chondromyxoid components identical in appearance to pleomorphic adenoma of the salivary gland

Sharply circumscribed
- Thick sclerotic pseudocapsule
- Tumor may penetrate capsule
Frequently intraductal
- Duct may be obliterated and recognized only on keratin or EVG stain
May be associated with papilloma
Mixture of epithelial, myoepithelial and chondromyxoid components
- Epithelial cells form acini, islands, ducts
  - Ducts lined by columnar to cuboidal cells
- Myoepithelial cells surround ducts and merge into stroma
  - Small bland oval or polyhedral cells
  - Eosinophilic cytoplasm
- Myxoid or chondromyxoid stroma
  - Contains stellate and spindled cells
  - May form hyaline cartilage
  - Occasional ossification
  - Rare adipose differentiation
No atypia or mitotic figures

Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting: May 1, 2006