Hybridization for HER2 testing in gastric carcinoma: a comparison of fluorescence in situ hybridization with a novel fully automated dual-color silver in situ hybridization

Fernando Lopez-Rios (1) , Elena Garcia-Garcia (1) , Carlos Gomez-Martin (2) , Barbara Angulo (1) , Esther Conde (1) , Ana Suarez-Gauthier (1) , Magdalena Adrados (3) , Cristian Perna (4) , Jose Luis Rodriguez-Peralto (5) , Manuel Hidalgo (1)

1 Laboratorio de Dianas Terapeuticas
2 Department of Oncology
3 Department of Pathology
4 Department of Pathology
5 Department of Pathology

Aims: Amplification of the human epidermal growth factor receptor 2 (HER2) gene has been reported in gastric carcinoma (GC). Accordingly, trastuzumab plus chemotherapy has recently become the new standard treatment for HER2 positive advanced GCs. Methods and results: We sought to compare the alleged gold standard for hybridization (FISH) with a novel fully automated brightfield dual-color silver enhanced in situ hybridization (SISH) in a series of 166 GC samples. Additionally, tumors with discordant results obtained by FISH and SISH were analyzed by real-time quantitative PCR with the LightMix kit HER2/neu. 17.5% and 21% of the samples were amplified by FISH and SISH, respectively. Heterogeneity was identified in up to 52% of the cases. In 96.4% of cases FISH showed the same results as SISH. All 6 discordant cases were positive by SISH and negative by FISH. On review of the FISH slides, all contradictory cases were polysomic and were confirmed to be negative for amplification by real-time PCR. Interestingly, all ratios in this latter group were between 2.06 and 2.50 so setting the cut-off for amplification at ≥ 3 resulted in a perfect concordance. Conclusions: Dual color SISH represents a novel method for the determination of HER2 status in GC.

Mots clés: Medicine

Fernando Lopez-Rios, Elena Garcia-Garcia, Carlos Gomez-Martin, Barbara Angulo, Esther Conde, et al.. Hybridization for HER2 testing in gastric carcinoma: a comparison of fluorescence in situ hybridization with a novel fully automated dual-color silver in situ hybridization. Histopathology, 2011, 59 (1), pp.8. ⟨10.1111/j.1365-2559.2011.03894.x⟩. ⟨hal-00661257⟩