2025 Volume 39 Issue 1 Pages 78-85
An 81-year-old female patient was presented with jaundice and pruritus. Abdominal contrast-enhanced computed tomography (CT) scan revealed a mass lesion in the distal bile duct. We performed ERCP and diagnosed the patient with extensive cholangiocarcinoma with horizontal extension from the distal bile duct to the anterior segment bile duct. We decided that pancreatoduodenectomy and resection of the right liver lobe would be difficult due to age and insufficient remaining liver capacity. After insertion of plastic stents in the left and right hepatic ducts, monotherapy with gemcitabine was started, but after 10 courses, CT showed an increase in tumor size. Cancer tissue taken before chemotherapy demonstrated microsatellite instability-high (MSI-H), and the patient was switched to Pembrolizumab monotherapy. The tumor had shrunk to a size that was invisible on CT after 7 courses. Therefore, active MSI-H testing might be useful.
