A 70-year-old woman was diagnosed poorly differentiated hepatocellular carcinoma (HCC), lymphocyte rich. In this case, programmed cell death 1 expression was observed. Immune checkpoint inhibitor treatment may be effective in such cases, although there have been no reports of their use for poorly differentiated HCC, lymphocyte-rich.

Pembrolizumab is considered to be an effective therapy for patients with microsatellite instability (MSI)-high cancer. Here, we report a case of MSI-high cholangiocarcinoma effectively treated with pembrolizumab. MSI status should be actively evaluated in patients with cholangiocarcinoma.