Detection of ALK rearrangement by immunohistochemistry in lung adenocarcinoma and the identification of a novel EML4-ALK variant

J Thorac Oncol. 2013 Jul;8(7):883-91. doi: 10.1097/JTO.0b013e3182904e22.


Introduction: The echinoderm microtubule-associated protein-like 4 anaplastic lymphoma kinase (EML4-ALK) fusion gene has been identified as a potent oncogenic driver in non-small-cell lung cancer, in particular adenocarcinoma (ADC). It defines a unique subgroup of lung ADC, which may be responsive to ALK inhibitors. Detection of ALK rearrangement by fluorescence in situ hybridization (FISH) or reverse transcriptase polymerase chain reaction (RT-PCR) is considered to be the standard procedure, but each with its own limitation. We evaluated the practical usefulness of immunohistochemistry (IHC) to detect ALK expression as a reliable detection method of ALK rearrangement in lung ADC.

Methods: We tested 373 lung ADCs for ALK rearrangement by IHC and FISH. Multiplex RT-PCR was performed to confirm the fusion variants.

Results: Twenty-two of 373 lung ACs (5.9%) were positive for ALK immunoreactivity. ALK-positive tumor cells demonstrated strong and diffused granular staining in the cytoplasm. All the ALK IHC-positive cases were confirmed to harbor ALK rearrangement, either by FISH, or RT-PCR. Two cases with positive ALK protein expression, but negative for breakapart FISH signal were shown to harbor EML4-ALK variant 1 by RT-PCR. None of the ALK IHC-negative cases were FISH-positive. In addition, we identified a novel EML4-ALK fusion variant (E3:ins53A20), and its potent transformation potential has been confirmed by in vivo tumorigenicity assay.

Conclusion: IHC can effectively detect ALK rearrangement in lung cancer. It might provide a reliable and cost-effective diagnostic approach in routine pathologic laboratories for the identification of suitable candidates for ALK-targeted therapy.

MeSH terms

  • Adenocarcinoma / diagnosis
  • Adenocarcinoma / genetics*
  • Adult
  • Aged
  • Aged, 80 and over
  • Anaplastic Lymphoma Kinase
  • Animals
  • Carcinoma, Non-Small-Cell Lung / diagnosis
  • Carcinoma, Non-Small-Cell Lung / genetics*
  • Cell Transformation, Neoplastic
  • Cohort Studies
  • Female
  • Follow-Up Studies
  • Gene Rearrangement*
  • Genetic Variation
  • Humans
  • Immunoenzyme Techniques
  • In Situ Hybridization, Fluorescence
  • Lung Neoplasms / diagnosis
  • Lung Neoplasms / genetics*
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Middle Aged
  • NIH 3T3 Cells
  • Neoplasm Grading
  • Neoplasm Staging
  • Oncogene Proteins, Fusion / genetics*
  • Prognosis
  • RNA, Messenger / genetics
  • Receptor Protein-Tyrosine Kinases / genetics*
  • Reverse Transcriptase Polymerase Chain Reaction


  • EML4-ALK fusion protein, human
  • Oncogene Proteins, Fusion
  • RNA, Messenger
  • ALK protein, human
  • Alk protein, mouse
  • Anaplastic Lymphoma Kinase
  • Receptor Protein-Tyrosine Kinases