As we study HER2 activity in novel settings with novel drugs (including trastuzumab-deruxtecan and other antibody-drug conjugates with activity in HER2-low settings), keeping a broad view of methods of evaluating HER2 (tissue IHC, tissue FISH, tissue NGS, ctDNA, expression on circulating tumor cells), their correlation, and their ability to predict benefit is important [28, 29]. This evidence concerns the gene ERBB2 and neoplasm.