Recently, the ToGA (Trastuzumab for Gastric Cancer) trial evaluated the role of trastuzumab (Herceptin®) in human epidermal growth factor receptor 2 (HER2) over-expressing gastric and gastroesophageal junction (GEJ) adenocarcinoma and showed improvement in overall survival when trastuzumab was added to the standard chemotherapy compared to standard chemotherapy without trastuzumab. This evidence concerns the gene ERBB2 and adenocarcinoma.