Clinicians who discover GNET during gastroscopy, especially in patients with concurrent iron deficiency anemia, autoimmune thyroid disease or other autoimmune diseases, should pay close attention to the presence of gastric mucosal atrophy and further perform tests for gastrin, PG, PCA, IFA, etc., to assess the possibility of AIG. The gene discussed is GAST; the disease is gastric neuroendocrine tumor, well differentiated, low or intermediate grade.