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-?xed paraf?n-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.