Background:Composite gangliocytoma/neuroma and neuroendocrine tumor (CoGNET) is a rare neoplasm typically arising in the second portion of the duodenum.¹˒² Its occurrence in young adults and its association with pancreatic anatomical variants are poorly documented. We report the case of a young woman with Neurofibromatosis type I (NF1), pancreas divisum, and recurrent pancreatitis who was incidentally found to have a duodenal CoGNET.
Case Presentation:A 22-year-old woman with NF1 had been followed since 2016 for recurrent acute pancreatitis. Secretin-enhanced MRCP demonstrated pancreas divisum, and between 2017 and 2021 she underwent multiple ERCPs.
Serial imaging from 2021 to 2024 showed a mildly dilated but stable dorsal duct with features of chronic pancreatitis and no focal lesions. In September 2025, follow-up contrast-enhanced MRI revealed the new onset of a well-circumscribed, hypervascular solid nodule (23 × 25 mm) between the pancreatic uncinate process and the third duodenal portion.
Endoscopic ultrasound confirmed a 25-mm oval, hypoechoic, hypervascular lesion on eFlow, showing a distinct compressive effect on the uncinate process on endosonographic evaluation and mild endoluminal deformity on endoscopic inspections. EUS-guided fine-needle biopsy was performed using a 22-gauge needle with three passes. Histopathologic analysis demonstrated a well-differentiated neuroendocrine neoplasm with mixed spindle–epithelioid morphology and strong SST2A expression, consistent with a CoGNET.
Discussion:CoGNET is an uncommon entity with very few cases reported, and nearly all published diagnoses have historically been made on surgical specimens. Its coexistence with pancreas divisum and NF1 has not previously been described. Importantly, the role of EUS-guided tissue acquisition in diagnosing CoGNET is virtually absent from current literature, with no dedicated studies or standardized criteria. This case highlights that EUS-FNB may represent a valuable, under-recognized tool for early diagnosis of CoGNET.
Conclusion:This case illustrates a rare duodenal CoGNET identified incidentally during long-term follow-up for chronic pancreatitis in a young woman with NF1 and pancreas divisum. The effective use of EUS-guided FNB to obtain a definitive histologic diagnosis underscores a diagnostic pathway largely absent from the current literature. Increasing awareness of this entity and recognition of its key EUS and FNB characteristics can significantly influence clinical decision-making, surgical planning, and long-term outcomes.