title: HER2 status in lung adenocarcinoma: a comparison of immunohistochemistry, fluorescence in situ hybridization (FISH), dual-ISH, and gene mutations.
abstract: OBJECTIVE
  While novel anti-human epidermal growth factor receptor 2 (HER2) agents have recently been developed, no definite criteria have been proposed as indications for the use of these agents in patients with lung cancer. Here, we tested HER2 alterations by using four methods and explored the concordance of these methods to improve our understanding of the accuracy of HER2 testing methods.
  
  
  METHODS
  We analyzed HER2 protein expression by immunohistochemistry (IHC) and HER2 amplification by fluorescence in situ hybridization (FISH) and dual in situ hybridization (DISH) by using a tissue microarray comprising lung adenocarcinoma specimens from 243 consecutive patients. The presence of mutations in the EGFR, KRAS, and HER2 genes were also determined.
  
  
  RESULTS
  Positive IHC (score 3+) was observed in six cases (2.5%). Amplification of HER2 was observed in five cases (2.1%) by FISH and in nine cases (3.7%) by DISH. HER2 expression by IHC and gene amplification by FISH were significantly associated (P<0.001). The overall concordance between FISH and DISH by amplification status was 96.7% (P<0.001). One hundred nine tumors (49.9%) had EGFR mutations, 25 (11.2%) had KRAS mutations, and six (2.7%) had HER2 mutations. All of these mutations were mutually exclusive. Cases having HER2 mutations were positively correlated with cases having HER2 amplification (P<0.001). Two of six cases with HER2 mutations showed amplifications by FISH and DISH tests.
  
  
  CONCLUSIONS
  HER2 protein overexpression, gene amplification, and gene mutations appeared to be uncommon in lung adenocarcinoma. Cases with HER2 mutations tended to show HER2 gene amplification. The results indicated that HER2 gene amplification and mutations should be tested to determine whether patients are eligible for administration of new anti-HER2 agents. In addition, DISH was better than FISH for detection of cases with HER2 amplification.
authors.affiliation: Department of Laboratory Medicine, Shinshu University Hospital, Matsumoto, Japan; Department of Diagnostic Pathology, Kyoto University Hospital, Kyoto, Japan. Electronic address: akyoshi@shinshu-u.ac.jp.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yoshizawa
authors.affiliation: Department of Diagnostic Pathology, Kyoto University Hospital, Kyoto, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Sumiyoshi
authors.affiliation: Department of Thoracic Surgery, Kyoto University Hospital, Kyoto, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Sonobe
authors.affiliation: Department of Thoracic Surgery, Kyoto University Hospital, Kyoto, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Kobayashi
authors.affiliation: Department of Laboratory Medicine, Shinshu University Hospital, Matsumoto, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Uehara
authors.affiliation: Department of Diagnostic Pathology, Kyoto University Hospital, Kyoto, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Fujimoto
authors.affiliation: Department of Diagnostic Pathology, Kyoto University Hospital, Kyoto, Japan.
authors.forename: Tatsuaki
authors.initials: T
authors.lastname: Tsuruyama
authors.affiliation: Department of Thoracic Surgery, Kyoto University Hospital, Kyoto, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Date
authors.affiliation: Department of Diagnostic Pathology, Kyoto University Hospital, Kyoto, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Haga
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis / Q000235:genetics* / Q000378:metabolism*; D000077192:Adenocarcinoma of Lung; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D066246:ErbB Receptors / Q000235:genetics; D005260:Female; D005784:Gene Amplification; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008175:Lung Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D060787:Neoplasm Grading; D009367:Neoplasm Staging; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism*; D012307:Risk Factors; D047368:Tumor Burden; D055815:Young Adult
chemical_list: D066246:ErbB Receptors; D016283:Proto-Oncogene Proteins p21(ras); D018719:Erb-b2 Receptor Tyrosine Kinases
keywords: Dual in situ hybridization; Fluorescence in situ hybridization; Human epidermal growth factor receptor 2; Immunohistochemistry; Lung adenocarcinoma; Trastuzumab