title: Cytokeratin 5/6 immunohistochemistry assists the differential diagnosis of atypical proliferations of the breast.
abstract: OBJECTIVE
  This study was performed to determine the diagnostic value of keratin 5/6 (CK 5/6) immunophenotyping on routinely processed breast tissues.
  
  
  RESULTS
  Six hundred and ninety-nine breast lesions, including normal tissues as well as benign and malignant lesions in 321 formalin-fixed, paraffin-embedded samples from 158 different patients were investigated immunohistochemically, following wet autoclave pre-treatment for antigen retrieval. In normal breast tissues, both myoepithelial and luminal epithelial cells expressed CK 5/6 in varying amounts. While myoepithelial immunoreactivity was most pronounced in the duct system, luminal epithelial immunoreactivity was strongest in the terminal duct lobular units. In ductal hyperplasias (DH), luminal epithelial cells predominantly revealed CK 5/6 immunoreaction. In contrast, neoplastic epithelial cells in atypical ductal and lobular hyperplasias (ADH and ALH) lacked such an expression, whereas in ductal in-situ carcinomas (DCIS) and in infiltrating ductal carcinomas 3.7% and 7.7%, of the cases respectively, showed positive immunostaining for CK 5/6.
  
  
  CONCLUSIONS
  Immunophenotyping of keratin 5/6 expression can be helpful in the diagnosis of atypical hyperplasias and in-situ carcinomas of the breast. It is particularly valuable in the differential diagnosis between benign and atypical proliferative lesions.
authors.affiliation: Gerhard-Domagk-Institute of Pathology, University of Münster, Department of Pathology, City Hospital, Osnabrück, and City Hospital, Berlin-Buch, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Otterbach
authors.forename: A
authors.initials: A
authors.lastname: Bànkfalvi
authors.forename: S
authors.initials: S
authors.lastname: Bergner
authors.forename: T
authors.initials: T
authors.lastname: Decker
authors.forename: R
authors.initials: R
authors.lastname: Krech
authors.forename: W
authors.initials: W
authors.lastname: Boecker
mesh_terms: D001940:Breast / Q000378:metabolism / Q000473:pathology*; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D002278:Carcinoma in Situ / Q000378:metabolism / Q000473:pathology; D002455:Cell Division; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D006965:Hyperplasia / Q000378:metabolism / Q000473:pathology; D007150:Immunohistochemistry; D007633:Keratins / Q000032:analysis*; D009361:Neoplasm Invasiveness
chemical_list: D007633:Keratins