HER2 status is assessed using immunohistochemistry (IHC) to evaluate receptor expression on the cell surface and in situ hybridization (ISH) to confirm gene amplification, with the same criteria of gastric cancer (IHC 0: Negative expression, IHC 1+: Weak expression IHC 2+: Moderate expression (requires ISH confirmation) IHC 3+: Strong expression (HER2-positive) [33,34]. Here, ERBB2 is linked to gastric cancer.