Embryonal Rhabdomyosarcoma of the Biliary Tract Masquerading as Type IV Choledochal Cyst: A Radiodiagnostic Challenge

Embryonal rhabdomyosarcoma (ERMS) of the biliary tract is an exceptionally rare pediatric malignancy that may mimic benign obstructive biliary disorders. We report a 4-year-old male presenting with progressive abdominal distension, jaundice, and edema. Cross-sectional imaging demonstrated diffuse intrahepatic and extrahepatic biliary dilatation consistent with type IV choledochal cyst, associated with intraductal septated contents and communicating intrahepatic lesions suggestive of cholangitis. No discrete enhancing mass was identified. Liver stiffness assessment indicated chronic liver disease. The patient underwent choledochal cyst excision with hepaticojejunostomy. Histopathology revealed ERMS of the biliary tract with immunopositivity for desmin, myogenin, and MyoD1. This case highlights a significant radiologic pitfall where biliary rhabdomyosarcoma may present without a discernible enhancing mass, underscoring the need for heightened suspicion in atypical pediatric obstructive jaundice.