A Rare Pediatric Intraductal Papillary Mucinous Neoplasm Presenting as a Pancreatic Pseudocyst With Splenic Vein Thrombosis and Gastric Variceal Hemorrhage.

Intraductal papillary mucinous neoplasm (IPMN) is a rare pancreatic cystic neoplasm in children. Pediatric pancreatic cystic lesions are more often inflammatory, traumatic, or congenital; therefore, IPMN may be mistaken for pseudocysts or pancreatitis-related changes. We report the case of a 15-year-old girl who initially presented with intermittent abdominal pain, mild lipase elevation, and a pancreatic tail cyst that was managed as a presumed pseudocyst after interval regression on surveillance imaging. Despite initial improvement, she later developed upper gastrointestinal bleeding. Subsequent evaluation demonstrated progressive cyst enlargement, splenic vein thrombosis, splenomegaly, collateral vessel formation, and isolated gastric varices consistent with sinistral portal hypertension. Ultrasound and cross-sectional imaging confirmed progression of the pancreatic lesion, and endoscopic ultrasound with biopsy established the diagnosis of branch-duct IPMN. Following immunization against encapsulated organisms, the patient underwent robotic-assisted distal pancreatectomy with splenectomy. Surgical pathology confirmed a large branch-duct IPMN without invasive carcinoma. Recovery was uncomplicated, and follow-up showed no evidence of recurrence. This case highlights the diagnostic challenges of pediatric IPMN, particularly when it mimics a pancreatic pseudocyst and demonstrates apparent interval regression. It also illustrates the potential for significant vascular complications, including splenic vein thrombosis, sinistral portal hypertension, and gastric variceal hemorrhage. Persistent or evolving pancreatic cystic lesions in children warrant ongoing reassessment, especially when accompanied by vascular abnormalities. Early recognition and definitive management may prevent substantial morbidity and facilitate timely treatment of this rare pediatric pancreatic neoplasm.