Dissemination along the hepatocaval ligament in a caudate-origin intrahepatic cholangiocarcinoma: a case report with video.

Intrahepatic cholangiocarcinoma (iCCA) is an aggressive biliary malignancy in which complete surgical resection remains the only potentially curative treatment. Caudate lobe tumours are particularly challenging because of their proximity to major vascular structures, including the inferior vena cava (IVC). Although iCCA commonly spreads through vascular, lymphatic, perineural, and biliary pathways, extension along retrohepatic ligamentous planes has not previously been described. We present a 56-year-old man with caudate-origin iCCA and bulky nodal disease causing biliary obstruction. Following neoadjuvant gemcitabine, cisplatin, and pembrolizumab, the patient underwent an open right hepatectomy with caudate resection and lymphadenectomy. Intraoperatively, the tumour demonstrated retrocaval extension along the hepatocaval ligament posterior to the IVC, representing a previously unreported dissemination pathway. En bloc resection achieved negative margins. This case expands the current understanding of iCCA tumour behaviour and highlights the importance of recognizing retrohepatic ligamentous extension during surgical resection.