Considering the role of ERBB2d16 in the therapeutic resistance of HER2-overexpressing G/GEJ adenocarcinomas has not been well described, in the present study, we analyzed the expression of ERBB2d16 and markers of EMT (E-cadherin, vimentin) in tumors from 110 patients with HER2 positive gastric cancer who had been treated with standard chemotherapy plus trastuzumab and explored the correlation of ERBB2d16 expression with EMT, intratumoral infiltration of immune cells along with TCR repertoire diversity, and prognosis. The gene discussed is ERBB2; the disease is gastric cancer.