• HER2 | Gastric cancer HER2 is a protein that plays a critical role in the regulation of cell growth and differentiation and overexpression or amplification of HER2 is found in a subset of gastric cancers having significant implications for treatment and prognosis. HER2 is a receptor tyrosine kinase that, when overexpressed or amplified, promotes tumor cell proliferation, survival, and metastasis through activation of downstream signaling pathways like PI3K/AKT and MAPK. HER2-positive gastric cancer can be targeted with therapies that specifically inhibit HER2, thus blocking the growth-promoting signals. Approximately 15-20% of gastric cancers exhibit HER2 overexpression or amplification, making it a significant subset of the disease. HER2positive gastric cancer is often associated with more aggressive disease and poorer prognosis, although HER2-targeted therapies can improve outcomes. Trastuzumab (Herceptin), a monoclonal antibody, is the first HER2-targeted therapy approved for HER2-positive advanced gastric cancer, typically used in combination with chemotherapy.