title: Anaplastic lymphoma kinase (ALK) gene rearrangement in non-small cell lung cancer (NSCLC): results of a multi-centre ALK-testing.
abstract: BACKGROUND
  The reliable identification of non-small cell lung cancers (NSCLC) with chromosomal breaks in the gene of the anaplastic lymphoma kinase (ALK) is crucial for the induction of therapy with ALK-inhibitors. In order to ensure a reliable detection of ALK-breaks by means of fluorescence in situ hybridization (FISH) testing, round robin tests are essential. In preparation of a nation (German)-wide round robin test we initiated a pre-testing phase involving 8 experts in FISH-diagnostics to identify NSCLC cases (n = 10) with a pre-tested ALK-status. In addition, ALK immunohistochemistry (IHC) was performed to assess ALK protein expression.
  
  
  METHODS
  Sections derived from a tissue microarray, each consisting of 3 cores from 10 NSCLC cases, were independently tested for ALK protein expression by IHC and genomic ALK-breaks by FISH involving 8 institutes of pathology. Based on a pre-screening, 5 cases were identified to be clearly ALK-break negative, whereas the remaining 5 cases were ALK-break positive including one case with low percentage (20%) of positive cells. The latter had been additionally tested by RT-PCR.
  
  
  RESULTS
  The 5 unequivocal ALK-break negative NSCLC were almost consistently scored negative by means of FISH and IHC by all 8 experts. Interestingly, 4 of the 5 cases with pre-defined ALK-breaks revealed homogenous FISH results whereas IHC for the detection of ALK protein expression showed heterogeneous results. The remaining case (low number of ALK-break positive cells) was scored negative by 3 experts and positive by the other 5. RT-PCR revealed the expression of an EML4-ALK fusion gene variant 1.
  
  
  CONCLUSIONS
  ALK-break negative NSCLC cases revealed concordant homogeneous results by means of FISH and IHC (score 0-1) by all 8 experts. Discordant FISH results were raised in one ALK-break positive case with a low number of affected tumor cells. The remaining 4 ALK-break positive cases revealed concordant FISH data whereas the ALK-IHC revealed very diverse results. The cases with concordant FISH results provide an excellent basis for round robin ALK-FISH testing. As long as standardized ALK-IHC protocols are missing, ALK protein expression cannot by regarded as the method of choice for identification of patients eligible for treatment with ALK inhibitors.
authors.affiliation: Institute of Pathology, Campus Charité Mitte, Charité Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany. maximilian.von-laffert@charite.de
authors.forename: Maximilian
authors.initials: M
authors.lastname: V Laffert
authors.forename: Arne
authors.initials: A
authors.lastname: Warth
authors.forename: Roland
authors.initials: R
authors.lastname: Penzel
authors.forename: Peter
authors.initials: P
authors.lastname: Schirmacher
authors.forename: Danny
authors.initials: D
authors.lastname: Jonigk
authors.forename: Hans
authors.initials: H
authors.lastname: Kreipe
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Schildhaus
authors.forename: Sabine
authors.initials: S
authors.lastname: Merkelbach-Bruse
authors.forename: Reinhard
authors.initials: R
authors.lastname: Büttner
authors.forename: Simone
authors.initials: S
authors.lastname: Reu
authors.forename: Rosi
authors.initials: R
authors.lastname: Kerler
authors.forename: Andreas
authors.initials: A
authors.lastname: Jung
authors.forename: Thomas
authors.initials: T
authors.lastname: Kirchner
authors.forename: Cornelius
authors.initials: C
authors.lastname: Wölfel
authors.forename: Iver
authors.initials: I
authors.lastname: Petersen
authors.forename: Regulo
authors.initials: R
authors.lastname: Rodriguez
authors.forename: Wolfram
authors.initials: W
authors.lastname: Jochum
authors.forename: Holger
authors.initials: H
authors.lastname: Bartsch
authors.forename: Annette
authors.initials: A
authors.lastname: Fisseler-Eckhoff
authors.forename: Erika
authors.initials: E
authors.lastname: Berg
authors.forename: Dido
authors.initials: D
authors.lastname: Lenze
authors.forename: Manfred
authors.initials: M
authors.lastname: Dietel
authors.forename: Michael
authors.initials: M
authors.lastname: Hummel
mesh_terms: D000077548:Anaplastic Lymphoma Kinase; D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D015321:Gene Rearrangement; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence / Q000379:methods; D008175:Lung Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics*
chemical_list: C000626173:ALK protein, human; D000077548:Anaplastic Lymphoma Kinase; D020794:Receptor Protein-Tyrosine Kinases
keywords: Anaplastic lymphoma kinase (ALK) gene rearrangement; Fluorescence in situ hybridization (FISH); Immunohistochemistry (IHC); Non-small cell lung cancer (NSCLC); Round robin test