S3454 Ectopic Pancreas With Pseudocyst: An Elusive Cause of Recurrent Abdominal Pain

Introduction: Ectopic pancreas (EP), or pancreatic rest, refers to pancreatic tissue located outside the usual anatomical location. EP is a congenital anomaly identified in 1%–2% of autopsies and is usually asymptomatic. Case Description/Methods: A 47-year-old man with gastroesophageal reflux, peptic ulcer disease, and hepatic cysts presented with chronic episodic nausea, vomiting, abdominal pain, and weight loss. Laboratory tests showed a normal lipase level (34 U/L) and normal liver enzymes. Magnetic resonance imaging showed a 12.7 × 7.5 × 7.7 cm complicated fluid collection with a thick wall and internal debris in the right upper quadrant. Wall thickening of the gastric antrum and the first portion of the duodenum was present. Endoscopic ultrasound showed a 13 mm by 16 mm submucosal nodule in the gastric antrum that was hypoechoic and contained anechoic tubular structures. A large anechoic cyst extended from the perigastric space close to the ectopic pancreas to the right upper quadrant gallbladder fossa. Fine needle aspiration of the cyst revealed amorphous debris, cloudy yellow fluid with high amylase (4897 U/L), low CEA (93 ng/mL), high lipase (16,700 U/L), and negative cytology, consistent with a pancreatic pseudocyst arising from EP tissue. The patient felt better after cyst aspiration and ultimately underwent an elective exploratory laparotomy involving excision of the cyst, distal gastrectomy of the EP, and Roux-en-Y gastrojejunostomy reconstruction. Intraoperatively, there were dense adhesions in the right upper quadrant from recurrent pseudocyst formation, the native pancreas appeared healthy, and the pseudocyst measured 6-7 cm with necrotic tissue but no signs of infection. Pathology of the stomach with a focus on ectopic pancreas revealed changes of chronic pancreatitis and pseudocyst formation, which were negative for malignancy. His chronic symptoms of abdominal pain and bloating resolved on follow-up evaluations. Discussion: This case highlights the rare manifestation of gastric ectopic pancreas tissue behaving like acute pancreatitis, resulting in the formation of a large pancreatic pseudocyst. Diagnosis required a combination of serial imaging, endoscopic evaluation, and surgical exploration. Importantly, EP should remain in the differential diagnosis for ambiguous upper gastrointestinal cystic lesions even in the absence of a classic history of pancreatitis. Early recognition may help guide targeted interventions and definitive management with surgical resection.