Early-onset extrahepatic cholangiocarcinoma in a young adult with a resected congenital biliary cyst: a rare case report.

Introduction: Congenital choledochal cysts are well-recognized risk factors for subsequent hepatobiliary malignancy, particularly cholangiocarcinoma, even after surgical excision. However, the development of extrahepatic cholangiocarcinoma (eCCA) in early adulthood following neonatal resection of a congenital biliary cyst is exceptionally rare. We report a case of early-onset eCCA in a young woman who was previously treated surgically in the neonatal period. Case presentation: A 25-year-old woman with a history of neonatal resection of a congenital biliary cyst, cholecystectomy, and biliary-enteric jejunal anastomosis presented with progressive epigastric and left upper quadrant pain, postprandial vomiting, and marked weight loss. She had no jaundice, pruritus, or fever. At the age of 23, she had undergone further intervention for biliary stones, including endoscopic retrograde cholangiopancreatography, surgical stone extraction, and revision of the biliary-enteric anastomosis. Laboratory evaluation showed pancytopenia, microcytic anemia, preserved liver biochemistry, and elevated CA19-9. Magnetic resonance cholangiopancreatography demonstrated marked intrahepatic biliary dilatation with filling defects. Contrast-enhanced computed tomography revealed a large infiltrative upper abdominal mass invading the gastric wall and extending into the left hepatic lobe, with encasement of major vessels, portal hypertension, splenomegaly, ascites, and residual hilar biliary dilatation. Upper gastrointestinal (GI) endoscopy and endoscopic ultrasound showed extensive varices and an ulcerated gastric wall lesion caused by an external infiltrative mass. Endoscopic ultrasound-guided fine-needle aspiration demonstrated poorly differentiated invasive adenocarcinoma. Immunohistochemistry showed CK7 positivity and CK20 negativity, supporting a pancreatobiliary or upper GI origin. In the context of the patient's surgical history and clinicoradiologic findings, the tumor was considered most consistent with unresectable eCCA. The patient was started on systemic chemotherapy with oxaliplatin and 5-fluorouracil. Discussion: This case illustrates several unusual and clinically important features. First, cholangiocarcinoma occurred at an exceptionally young age despite neonatal surgical treatment of the congenital biliary cyst. Second, the tumor presented without jaundice or biochemical cholestasis despite advanced local disease. Third, the lesion radiologically and endoscopically mimicked a primary gastric malignancy, adding diagnostic complexity. The case supports the concept that malignant transformation may occur decades after apparently corrective surgery, possibly due to persistent epithelial injury, residual biliary abnormalities, and chronic inflammatory changes related to prior biliary-enteric reconstruction. Conclusion: Early-onset eCCA after childhood resection of a congenital biliary cyst is exceptionally rare but possible. This case highlights the persistent, lifelong malignant potential associated with choledochal cysts and emphasizes that advanced disease may develop in the absence of jaundice or abnormal liver biochemistry. Long-term and possibly lifelong surveillance should be considered, particularly in patients with residual biliary abnormalities or prior biliary-enteric reconstruction.