[Clinical significance of HER2 positivity in gallbladder adenocarcinoma]

Objective: To study the clinical significance of HER2 overexpression and/or amplification in gallbladder adenocarcinoma. Methods: HER2 staining was performed on 123 cases of gallbladder adenocarcinoma specimens by IHC using scoring criteria for gastric cancer. FISH test was performed on the IHC score 2+ and 3+ cases and the results were correlated with clinicopathological findings. Results: In total of 123 cases of gallbladder adenocarcinomas, HER2 amplification detection rate was 22.0%(27/123). Among 27 cases with HER2 gene amplification, 5 cases were IHC 2+ (5/12) and 22 cases were IHC 3+ (91.7%, 22/24), and the concordance rates between IHC and FISH were 41.7%and 91.7% respectively. The heterogeneity of HER2 expression was observed in 3 cases with complete strong cell membrane staining but the number of stained cells of<10%.Among them, 1 case showed HER2 gene amplification. The difference of HER2 gene amplification in well, moderately and lowly differentiated tumors has statistical significance(χ²=24.4, P<0.01), and its detection rate was related to the degree of tumor differentiation (C=0.45). Conclusions: About 20% gallbladder adenocarcinomas have HER2 positivity, providing the targeted therapy implicationfor these patients.IHC HER2 scoring system for gastric carcinoma is suitable for gallbladder carcinoma. However, the cases with complete strong membrane staining but in <10% tumor cells should be included in the 2+ score IHC group.