ERBB2 and neoplasm: Currently, there are no ideal and effective biomarkers for gastric cancer immunotherapy; microsatellite unstable (MSI‐H) and high tumor mutation burden in gastric cancers suggest that patients may benefit from immunotherapy.[43] Given that Her2‐positive gastric cancers have a low mutation burden,[44] immunotherapy is not recommended as first‐line treatment for this patient population in the existing guidelines.