title: Assessment of thin-layer breast aspirates for immunocytochemical evaluation of HER2 status.
abstract: OBJECTIVE
  To determine whether immunocytochemistry (ICC) for HER2 on ThinPrep (TP)-processed breast fine needle aspiration biopsies (Cytyc Corp., Boxborough, Massachusetts, U.S.A.) is comparable to the findings of immunohistochemistry on corresponding surgically removed tissue.
  
  
  METHODS
  Immunostaining was performed on 63 malignant breast fine needle aspirates and compared to immunostaining on paraffin sections (PSs) from the subsequent biopsies. The HercepTest (Dako, Carpinteria, California, U.S.A.) and TAB250 antibodies were utilized. Cases in which the TP and paraffin HER2 results did not correlate were further assessed for gene amplification by differential polymerase chain reaction (dPCR).
  
  
  RESULTS
  HER2 overexpression was found in 9 of the 63 cases (14%). TAB250 had higher specificity on PS versus TP (P = .008), and TAB250 had higher specificity on PS versus the HercepTest on PS and TP (P = .004 and .0001, respectively).
  
  
  CONCLUSIONS
  HER2 immunostaining with both the HercepTest and TAB250 on TP is unreliable due to low specificity (72% and 83% for HercepTest and TAB250, respectively). However, both antibodies have high sensitivity (89% and 100%, respectively); suggesting that this method may have some utility as a preliminary screening test for HER2 status. Negative HER2 staining by ICC is highly predictive of the absence of HER2 overexpression, whereas positive HER2 staining on TP would require further validation by either dPCR of fluorescence in situ hybridization.
authors.affiliation: Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Department of Laboratory Medicine and Pathobiology, University of Toronto. ybedard@mtsinai.on.ca
authors.forename: Yvan C
authors.initials: YC
authors.lastname: Bédard
authors.forename: Aaron F
authors.initials: AF
authors.lastname: Pollett
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Leung
authors.forename: Frances P
authors.initials: FP
authors.lastname: O'Malley
mesh_terms: D000906:Antibodies; D044963:Biopsy, Fine-Needle / Q000592:standards* / Q000706:statistics & numerical data; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D002277:Carcinoma / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000592:standards* / Q000706:statistics & numerical data; D015588:Observer Variation; D010340:Pathology, Surgical / Q000592:standards / Q000706:statistics & numerical data; D011237:Predictive Value of Tests; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis*; D015203:Reproducibility of Results; D016610:Tissue Embedding / Q000592:standards
chemical_list: D000906:Antibodies; D018719:Erb-b2 Receptor Tyrosine Kinases