Background/aim: Trastuzumab® is used for human epidermal growth factor receptor 2 (HER2)-overexpressing metastatic gastric/gastroesophageal junction (GEJ) adenocarcinoma. Our aim was to compare HER2 expression by immunohistochemistry (IHC) and dual in situ hybridization (DISH) in early-stage vs. late-stage gastric and GEJ tumors.
Materials and methods: Fifty early-stage and 50 late-stage gastric tumors and a similar number of early-stage and late-stage GEJ tumors were studied. HER2 was analyzed by IHC and dual-ISH using tissue microarray.
Results: Of 200 selected cases, 168 had satisfactory results. Among the 110 cases with both tests successfully performed, there were only five cases with discrepancy between assays (4.5%). Seven equivocal (2+) cases by IHC were all found to be amplified by dual-ISH. When compared with IHC, dual-ISH identified 12 additional HER2-positive cases (10.9%).
Conclusion: The 12.5% overall overexpression/amplification in gastric and GEJ adenocarcinomas is in concordance with previous reports. No correlation was found between tumor stage and HER2 overexpression/amplification. Determination of HER2 in limited tissue samples benefits from combinational IHC and ISH testing.
Keywords: DISH; HER2; esophageal cancer; gastric cancer.
Copyright© 2018, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.