In clinical practice, the general process for the histopathological diagnosis of GC is to evaluate the samples obtained by hematoxylin & eosin (H&E) staining, and then, in accordance with the HER2 testing guidelines proposed by the College of American Pathologists, the American Society for Clinical Pathology, and ASCO,[8] the NCCN Guidelines advocate for the utilization of immunohistochemistry (IHC) and, if necessitated, in situ hybridization (ISH) methodologies for the evaluation of HER2 status in GC. This evidence concerns the gene ERBB2 and gastric cancer.