HER2 Positive Gastric Cancer, Colorectal Cancer, Head and Neck Squamous Cell Carcinoma, EGFR Positive Solid Tumor, Advanced Solid Tumors, HER2-positive Breast Cancer, Hepatocellular Carcinoma, Non Small Cell Lung Cancer, Renal Cell Carcinoma, Pancreatic Cancer, Melanoma. This evidence concerns the gene EGFR and gastric cancer.