HER2 Gene Amplification by Fluorescence In Situ Hybridization (FISH) Compared With Immunohistochemistry (IHC) in 122 Equivocal Gastric Cancer Cases

Objective: To determine the frequency of HER2/neu amplification and the relationship between HER2/neu expression and clinicopathologic features in gastric cancers scored immunohistochemistry (IHC) 2+. Methods: A total of 122 gastric cancer cases scored IHC 2+ were retrospectively analyzed for HER2 amplification by fluorescence in situ hybridization (FISH). The correlation between HER2/neu expression and clinicopathologic features was analyzed. Results: HER2/neu gene was amplified in 17 out of the 122 gastric cancer samples. The concordance rate between IHC and FISH was 13.9%. HER2/neu status was correlated with the age of patients (P<0.05). Polysomy of CEP17 was demonstrated in 46 cases, 11 of which (23.91%) were amplified for HER2/neu. Within the subgroups, a correlation between CEP17 polysomy and the depth of invasion was observed (P<0.05). Conclusions: The results highlight the necessity of FISH test for further categorization when gastric cancer cases are scored 2+ by IHC. The value of HER2/neu for a potential role as a negative prognostic factor in the equivocal gastric cancer cases is limited.