ペリヒラー・肝臓外胆管癌の典型例および非典型例：剖検時の診断学的解明

Extrahepatic cholangiocarcinoma is a rare malignant neoplasm characterized by aggressive behavior and poor prognosis. It typically presents in the seventh to eighth decades of life, with a slight male predominance, and most commonly manifests with symptoms related to biliary obstruction; however, atypical clinical presentations may occur. We report the case of a 71-year-old man who presented with acute pancreatitis. Imaging studies failed to identify an underlying neoplasm, and the diagnosis was established only during the autopsy, which revealed a perihilar extrahepatic cholangiocarcinoma involving the proximal extrahepatic bile ducts, with extensive multiorgan infiltration. These findings accounted for the patient's atypical manifestations, including renal dysfunction and gastrointestinal bleeding, which were fully elucidated through postmortem examination. Extrahepatic cholangiocarcinoma represents a diagnostic challenge due to its nonspecific clinical features and its anatomically difficult location for biopsy, particularly when atypical manifestations predominate. This case highlights the value of autopsy in clarifying complex clinicopathologic correlations and provides observations regarding the role of immunohistochemistry in the diagnosis, prognostic assessment, and therapeutic management of these tumors.