In fact, the latest National Cancer Center Network (NCCN) guidelines on biliary tract cancer propose molecular profiling including microsatellite instability (MSI) or tumor mutation burden (TMB) for patients with unresectable or metastatic biliary tract cancer as a routine workup before initiating first-line treatment and three molecular markers (MSI-H, NTRK fusion, and RET fusion) and matched therapies are recommended as a treatment option of first-line chemotherapy [21]. The gene discussed is RET; the disease is neoplasm.