When Clinical Suspicion Overrides Benign Biopsy: Invasive Pancreatic Intraductal Oncocytic Papillary Neoplasm With Concurrent Neuroendocrine Tumor.

Intraductal oncocytic papillary neoplasms (IOPN) are rare pancreatic neoplasms. This is the case of a 76-year-old woman who presented with a large, symptomatic pancreatic head mass. Two separate endoscopic ultrasound-guided fine needle biopsies showed low-grade papillary neoplasm without invasive features, while final surgical pathology revealed invasive carcinoma arising from IOPN. In addition, a well-differentiated pancreatic neuroendocrine tumor was identified at the tumor interface, representing the first reported case of concomitant IOPN and neuroendocrine tumor. This case underscores the importance of multidisciplinary evaluation and the potential for fine needle biopsy to underestimate disease severity in IOPNs, which has critical implications for patient management.