Pilot evaluation of a HER2 testing in non-small-cell lung cancer.

Aims: HER2-positivity pattern in the specimens of immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH) has been hardly reported in non-small-cell lung cancer (NSCLC).

Methods: We evaluated the characteristics of HER2-positivity pattern in formalin-fixed paraffin-embedded samples using IHC and FISH in 15 patients enrolled in a larger prospective cohort study to survey a HER2-positive NSCLC.

Results: As for the immunostaining pattern, most specimens (79%) demonstrated incomplete or mixed-typed membranous immunoreactivity with heterogeneity, resembling that observed in gastric cancer rather than breast cancer. Concordance between IHC-positivity and FISH-positivity was 87.5% according to the criteria for breast cancer scoring system. On application of the gastric cancer scoring system to the examined tumours, the IHC score increased in the seven (43.8%) specimens, and the concordance between IHC positivity and FISH positivity rose to 93.8%.

Conclusions: In our pilot series, the pattern of IHC reactivity closely resembled that observed in gastric cancer rather than breast cancer.

Trial Registration Number: 000017003.