According to the registry data of C-CAT, the top five genes reported in FoundationOne®CDx Liquid in patients with biliary tract cancer were TP53, DNMT3A, ATM, CHEK2, and BRCA2, whereas they were TP53, CDKN2A, KRAS, CDKN2B, and ARID1A in FoundationOne®CDx. The gene discussed is TP53; the disease is biliary tract neoplasm.