Distal extrahepatic cholangiocarcinoma mimicking groove pancreatitis: A case report and literature review.

Background: The differential diagnosis between cholangiocarcinoma and groove pancreatitis is quite challenging. Groove pancreatitis is commonly misdiagnosed as periampullary tumors. We reported a case of distal extrahepatic cholangiocarcinoma mimicking groove pancreatitis. Case report: A 57-year-old male patient was transferred to our hospital after endoscopic retrograde cholangiopancreatography (ERCP) with stent placement in the common bile duct due to obstructive jaundice at a local hospital. Groove pancreatitis was considered based on the clinical manifestations and multiple examinations [including computed tomography (CT), magnetic resonance cholangiopancreatography (MRCP), and endoscopic ultrasonography (EUS)]. The patient's symptoms and laboratory results almost returned to normal after conservative treatments. Interestingly, his symptoms and laboratory results worsened after the stent was removed. We performed a second EUS process and found a lesion in the lower common bile duct. Finally, the patient underwent pancreatoduodenectomy, and the diagnosis was confirmed as moderately differentiated adenocarcinoma of the common bile duct. Conclusion: Our case highlights the fact that distal extrahepatic cholangiocarcinoma, which is a malignant disease, can mimic a benign condition like groove pancreatitis. Our case also raises the concern that performing stent placement through ERCP to relieve jaundice without a clear diagnosis could interfere with further evaluation of the disease.