Successful pembrolizumab treatment of microsatellite instability‐high intrahepatic cholangiocarcinoma: A case report

Key Clinical Message The tumor reduction effect of pembrolizumab is extremely high compared to standard chemotherapy and might show prolonged survival. Therefore, the MSI status should be examined in patients with cholangiocarcinoma. Contrast‐enhanced computed tomography (CT) revealed a primary tumor (black arrow) before the initiation of pembrolizumab (A). After three cycles of pembrolizumab, the primary tumor showed a 32% reduction (B). After 14 cycles, the primary tumor shoed a 79% reduction (C).