Comparison of HER2 and Lauren Classification between Biopsy and Surgical Resection Samples, Primary and Metastatic Samples of Gastric Cancer

Purpose: Patients with advanced or metastatic adenocarcinoma of the stomach or esophagogastric junction for whom trastuzumab therapy is being considered, assessment for tumor human epidermal growth factor receptor-2 (HER2) status is necessary. Can the HER2 status and Lauren classification of the biopsy sample truly represent the HER2 status in the gastric cancer?