A Rare Case of Pancreatic Neuroendocrine Tumor with Intraductal Extension in the Dorsal Duct of a Pancreas Divisum

Background and Clinical Significance: Pancreatic neuroendocrine tumors (pNETs) rarely exhibit intraductal growth, a pattern that may mimic intraductal papillary mucinous neoplasms (IPMNs) or pancreatic ductal adenocarcinoma (PDAC). Preoperative recognition is challenging, particularly when associated with anatomic variants such as pancreas divisum. Case Presentation: A 63-year-old man with a history of pancreatic duct dilation presented with pruritus, weight loss, and lymphadenopathy. Cross-sectional imaging revealed a cephalopancreatic mass with upstream ductal dilatation. EUS demonstrated a hypervascular lesion with intraductal extension into the dorsal duct in the setting of pancreas divisum. EUS-FNB confirmed a well-differentiated pNET (G1) with loss of DAXX expression and preserved ATRX. Ga-68 PET/CT showed intense uptake in the primary lesion and lower-grade uptake in two additional nodules, later proven non-neoplastic. A multidisciplinary tumor board recommended preoperative optimization with somatostatin analog therapy and supervised weight reduction, followed by pylorus-preserving duodenocephalopancreatectomy. Final pathology confirmed NET G1 with intraductal growth and full concordance with preoperative EUS-FNB findings. Conclusions: in this case, a pNET showed intraductal growth within the dorsal duct in the context of pancreas divisus, further expanding the range of its reported presentations. It underscores the diagnostic value of EUS-FNB for morphologic, proliferative, and molecular characterization, and highlights the importance of multidisciplinary evaluation in guiding preoperative optimization and tailored surgical management.