Due to the emerging picture of tumoral heterogeneity of HER2 positive in particular and gastroesophageal cancers in general, larger datasets will be needed to ascertain if composite testing with traditional IHC/FISH, tumor NGS, and ctDNA, as well as other biomarkers, can enrich for patients that derive the most clinical benefit in HER2-directed strategies. This evidence concerns the gene ERBB2 and neoplasm.