Schwannoma of the common bile duct mimicking cholangiocarcinoma: a clinicoradiopathologic case report and literature review

Schwannoma of the biliary tract is an exceedingly rare benign neoplasm that can closely mimic cholangiocarcinoma, leading to significant diagnostic challenges. We report a 64-year-old woman who presented with right upper quadrant pain, anorexia and abnormal liver enzymes. Imaging studies demonstrated a common bile duct mass highly suspicious for malignancy, and cytologic evaluation of EUS-guided fine-needle aspiration was interpreted as adenocarcinoma. Based on these findings, pancreaticoduodenectomy was performed. Histopathological examination revealed a well-circumscribed spindle cell neoplasm with a characteristic plexiform growth pattern composed of bland spindle cells. Immunohistochemical analysis demonstrated diffuse and strong positivity for S-100 protein and SOX10, with negative staining for epithelial, smooth muscle, and gastrointestinal stromal tumor markers, establishing the diagnosis of plexiform schwannoma of the common bile duct. This case underscores the inherent limitations of preoperative imaging and EUS-FNA in submucosal biliary lesions, particularly in the setting of prior biliary stenting, where reactive epithelial changes may be misleading. Recognition of this rare entity and careful clinicoradiopathologic correlation are essential to avoid misdiagnosis and overtreatment.