HER2 overexpression was significantly high in males (p = 0.013), and HER2 expression was significantly more frequent in patients with differentiated gastric adenocarcinoma (well- and moderately differentiated adenocarcinomas) than in those with undifferentiated gastric adenocarcinoma (poorly differentiated adenocarcinoma and signet ring cell carcinoma) (p < 0.001). The gene discussed is ERBB2; the disease is gastric adenocarcinoma.