title: The use of stained cytologic direct smears for ALK gene rearrangement analysis of lung adenocarcinoma.
abstract: BACKGROUND
  Rearrangements involving the anaplastic lymphoma kinase (ALK) gene are present in approximately 5% of lung adenocarcinomas. Crizotinib is approved for the treatment of lung adenocarcinomas harboring ALK rearrangements. Patients with advanced stage lung cancer are not candidates for surgical resection of their primary tumors. For these patients, cytologic specimens often represent the only diagnostic tissue available. Cell blocks (CBs) are routinely used for molecular studies; however, insufficient CB cellularity can impede the performance of these assays.
  
  
  METHODS
  Thirty-two cytology cases of lung adenocarcinomas were analyzed by fluorescence in situ hybridization (FISH) for ALK rearrangements. Diff-Quik-stained smears were examined to identify tumor cell-enriched areas that were marked using a diamond-tipped scribe. Paired ALK rearrangement FISH was performed using smears and CBs in each case.
  
  
  RESULTS
  An ALK rearrangement was detected on direct smears and CB sections in 5 (16%) and 4 (13%), respectively, of the 32 cases studied. Concordant FISH results for smears and CBs were observed in 31 (97%) of 32 cases. In the 1 discordant case, an ALK rearrangement was detected on the direct smear but not in the CB. Reverse transcriptase-polymerase chain reaction analysis of this CB revealed the presence of an EML4-ALK rearrangement, thereby confirming a false-negative FISH result in the CB.
  
  
  CONCLUSIONS
  Stained cytologic direct smears can be effectively used for ALK rearrangement analysis by FISH. This approach represents a useful safeguard when insufficient CB cellularity is encountered and could prevent delays in treatment in this era of precision medicine.
authors.affiliation: Department of Pathology, University of Michigan Health System, Ann Arbor, Michigan.
authors.forename: Bryan L
authors.initials: BL
authors.lastname: Betz
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Dixon
authors.forename: Helmut C
authors.initials: HC
authors.lastname: Weigelin
authors.forename: Stewart M
authors.initials: SM
authors.lastname: Knoepp
authors.forename: Michael H
authors.initials: MH
authors.lastname: Roh
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis / Q000235:genetics*; D000077548:Anaplastic Lymphoma Kinase; D014408:Biomarkers, Tumor / Q000235:genetics*; D003581:Cytodiagnosis; D015321:Gene Rearrangement; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008175:Lung Neoplasms / Q000175:diagnosis / Q000235:genetics*; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D011379:Prognosis; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D014408:Biomarkers, Tumor; C522504:EML4-ALK fusion protein, human; D015514:Oncogene Proteins, Fusion; D012333:RNA, Messenger; C000626173:ALK protein, human; D000077548:Anaplastic Lymphoma Kinase; D020794:Receptor Protein-Tyrosine Kinases
keywords: adenocarcinoma; anaplastic lymphoma kinase (ALK) rearrangement; cytology; direct smear; fine-needle aspiration; fluorescence in situ hybridization; lung cancer; non-small cell lung cancer; precision medicine