Combined diagnosis of signet ring cell carcinoma of hilar cholangiocarcinoma by three endoscopes.

Signet-ring cell carcinoma is a poorly differentiated adenocarcinoma with a high degree of malignancy, which rarely occurs in hilar bile duct. As far as I know, this is the third signet-ring cell carcinoma of hilar cholangiocarcinoma found so far. We used endoscopic ultrasound（EUS） and per-oral cholangioscopy（POCPS） to make a definite diagnosis.