Ribonucleic Acid In Situ Hybridization Is a More Sensitive Method Than Immunohistochemistry in Detection of Thyroid Transcription Factor 1 and Napsin A Expression in Lung Adenocarcinomas

Arch Pathol Lab Med. 2016 Apr;140(4):332-40. doi: 10.5858/arpa.2014-0644-OA.


Context: TTF-1 and napsin A immunomarkers have a crucial role in differentiating lung adenocarcinoma from lung squamous cell carcinoma and in identifying a primary lung adenocarcinoma when working on a tumor of unknown origin.

Objectives: To investigate the diagnostic sensitivity of ribonucleic acid in situ hybridization (RNAscope) in the detection of expression of these biomarkers in lung adenocarcinomas and to compare RNAscope to immunohistochemical techniques.

Design: Both RNAscope and the immunohistochemical assays for TTF-1 and napsin A were performed on tissue microarray sections containing 80 lung adenocarcinomas and 80 lung squamous cell carcinomas. The RNAscope assay for both TTF-1 and napsin A was also performed on 220 adenocarcinomas from various organs.

Results: The RNAscope assay for TTF-1 gave positive results in 92.5% (74 of 80) of the lung adenocarcinomas; in contrast, immunohistochemistry gave positive results in 82.5% (66 of 80) of those cases. The RNAscope assay for napsin A gave positive results in 90% (72 of 80) of lung adenocarcinomas; immunohistochemistry results were positive in 77.5% (62 of 80) of those cases. Napsin A expression was not seen in lung squamous cell carcinomas by either method. In contrast, TTF-1 expression was seen in 3.8% (3 of 80) (1(+)) and 10% (8 of 80) (1(+)) of the squamous cell carcinomas by immunochemistry and the RNAscope, respectively. All nonpulmonary adenocarcinoma results were negative for TTF-1 by the RNAscope assay.

Conclusions: Preliminary data suggest that RNAscope is superior to immunohistochemistry in detecting TTF-1 and napsin A expression in primary lung adenocarcinomas. Therefore, performing an RNAscope assay may be considered for both TTF-1(-) and napsin A(-) cases with a clinical suspicion of lung adenocarcinoma. The TTF-1 results should be interpreted with caution because a small percentage of squamous cell carcinomas can be focally positive by either assay.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenocarcinoma / diagnosis*
  • Adenocarcinoma / metabolism
  • Adenocarcinoma of Lung
  • Aspartic Acid Endopeptidases / analysis
  • Biomarkers, Tumor / analysis*
  • Carcinoma, Non-Small-Cell Lung / diagnosis*
  • Carcinoma, Non-Small-Cell Lung / metabolism
  • Carcinoma, Squamous Cell / diagnosis*
  • Carcinoma, Squamous Cell / metabolism
  • Diagnosis, Differential
  • Humans
  • Immunohistochemistry
  • In Situ Hybridization / methods*
  • Lung / pathology
  • Lung Neoplasms / diagnosis*
  • Lung Neoplasms / metabolism
  • Nuclear Proteins / analysis
  • RNA, Neoplasm / analysis
  • Sensitivity and Specificity
  • Thyroid Nuclear Factor 1
  • Transcription Factors / analysis


  • Biomarkers, Tumor
  • NKX2-1 protein, human
  • Nuclear Proteins
  • RNA, Neoplasm
  • Thyroid Nuclear Factor 1
  • Transcription Factors
  • Aspartic Acid Endopeptidases
  • NAPSA protein, human