More recently, HER2 amplification/overexpression has also been identified in other solid tumors, such as gastric carcinomas (showing up to 20% with HER2 alterations), as well as in colorectal, salivary gland cancers, or uterine serous carcinomas, where anti-HER2 targeted therapy has also become the standard of care [32,33,34,35]. The gene discussed is ERBB2; the disease is endometrial serous adenocarcinoma.