ERBB2 and neoplasm: Thirteen patients had received circulating tumor DNA (ctDNA) analysis and next generation sequencing (NGS) test before the treatment of pyrotinib and ten of them showed gene abnormalities, including TP53 mutation (n = 7), ERBB2 amplification (n = 6), PIK3CA mutations (n = 3), Myc amplification (n = 3) and BRCA2 mutation (n = 2).