Adenoid Cystic Carcinoma of the Breast
Definition
- Very rare type of breast carcinoma resembling adenoid cystic carcinoma of other sites
Diagnostic Criteria
- Biphasic cell population
- One population with phenotype of duct lining cells
- Surrounds small lumens
- CK5/6, CK7, CK8/18, ckit positive
- Small cells with sparse cytoplasm and indistinct nucleoli
- One population with phenotype of myoepithelial cells
- Surrounds many nests and basement membrane cores
- p63, actin positive
- Various growth patterns, usually at least focally cribriform
- Biphasic, cylindromatous
- Cribriform growth surrounding cores of basement membrane material
- PASd positive
- Continuous with surrounding basement membrane
- Indistinct true lumens, frequently discernable only on immunohistologic stains
- Trabecular
- Tubular
- Solid (predominantly myoepithelial cells)
- Basaloid (predominantly lumenal cells)
- Rarely exhibits sebaceous or squamous differentiation
- Frequently grossly circumscribed but microscopically invasive
- May be multifocal
