title: Aberrant anaplastic lymphoma kinase expression in high-grade pulmonary neuroendocrine carcinoma.
abstract: OBJECTIVE
  In lung cancer with anaplastic lymphoma kinase (ALK) gene rearrangement, accurate diagnosis is essential to identify patients who can be treated with a specific kinase inhibitor. Sensitive ALK immunostaining can provide nearly complete concordance with gene rearrangement status and is expected to serve as a surrogate biomarker for tailored treatment with an ALK inhibitor. In the present report, we describe aberrant ALK expression in a small proportion of pulmonary neuroendocrine carcinomas (NECs) that do not have ALK gene alteration.
  
  
  METHODS
  A total of 227 pulmonary NECs were assembled on tissue microarrays and were subjected to highly sensitive ALK staining methods.
  
  
  RESULTS
  We observed focal positivity with heterogeneous intensity in 2 (2.9%) of 69 small-cell carcinomas and 1 (0.9%) of 106 large-cell NECs. In contrast, 52 carcinoid tumours were all negative for ALK expression. Neither ALK rearrangement nor amplification was observed using fluorescence in situ hybridisation, and no somatic mutation was detected in three ALK positive NECs.
  
  
  CONCLUSIONS
  Thus, this aberrant expression is probably of a wild-type ALK and a potential pitfall when implementing sensitive ALK immunohistochemistry in the molecular diagnosis of lung cancer.
authors.affiliation: Department of Pathology and Clinical Laboratories, National Cancer Center Hospital, Tokyo, Japan.
authors.forename: Harumi
authors.initials: H
authors.lastname: Nakamura
authors.forename: Koji
authors.initials: K
authors.lastname: Tsuta
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yoshida
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Shibata
authors.forename: Susumu
authors.initials: S
authors.lastname: Wakai
authors.forename: Hisao
authors.initials: H
authors.lastname: Asamura
authors.forename: Koh
authors.initials: K
authors.lastname: Furuta
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tsuda
mesh_terms: D000077548:Anaplastic Lymphoma Kinase; D014408:Biomarkers, Tumor / Q000378:metabolism*; D018278:Carcinoma, Neuroendocrine / Q000201:enzymology* / Q000473:pathology; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology* / Q000473:pathology; D060787:Neoplasm Grading; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*
chemical_list: D014408:Biomarkers, Tumor; C000626173:ALK protein, human; D000077548:Anaplastic Lymphoma Kinase; D020794:Receptor Protein-Tyrosine Kinases
keywords: Immunohistochemistry; Lung; Neuroendocrine Tumours