title: Diagnostic role of immunohistochemistry in the evaluation of breast pathology specimens.
abstract: BACKGROUND
  Immunohistochemistry plays a vital role in the evaluation of breast pathology specimens.
  
  
  OBJECTIVE
  To discuss the role of myoepithelial cell markers in the evaluation of various breast lesions. Other markers, such as E-cadherin and those used to differentiate mammary carcinoma from metastatic tumors to the breast, and markers used in the differential diagnosis of Paget disease, are also discussed.
  
  
  METHODS
  Data were obtained from review of the pertinent peer-reviewed literature.
  
  
  CONCLUSIONS
  Myoepithelial cell markers vary in their sensitivity and specificity, and one should be aware of the potential pitfalls in interpretation. Using panels of 2 or more myoepithelial cell markers is always recommended, either singly or in cocktail forms. Although negative E-cadherin staining supports the diagnosis of lobular origin, positive staining does not rule it out. Immunohistochemistry can be helpful in differentiating Paget disease from its mimics. Although metastatic tumors to the breast are rare, a triple-negative immunophenotype and absence of an in situ component should be a "red flag" for such possibility, especially in patients with clinical history of an extramammary malignancy.
authors.affiliation: From the Department of Pathology, University of Massachusetts, UMass Memorial Medical Center, Worcester, Massachusetts.
authors.forename: Larry
authors.initials: L
authors.lastname: Zhao
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Yang
authors.forename: Ashraf
authors.initials: A
authors.lastname: Khan
authors.forename: Dina
authors.initials: D
authors.lastname: Kandil
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis*; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods*
chemical_list: D014408:Biomarkers, Tumor