Pancreatic heterotopy, a rare entity, is defined as pancreatic tissue lying outside its normal location without anatomical or vascular connections with the pancreas proper. Cystic dystrophy is an uncommon and serious complication of heterotopic pancreas, usually in younger men. The mechanism by which cystic dystrophy develops is poorly understood. It is difficult to diagnose, as lesions deeper in the submucosa or the muscularis propria, are difficult to biopsy. We present an interesting and rare case of pancreatic heterotopia with cystic dystrophy of the duodenal wall, where endoscopic ultrasound clearly shows cystic changes in deeper layers of duodenum, later confirmed by surgery. Case: A 54-yr-old white male presented to the hospital after several bouts of abdominal pain. Prior to presentation, he experienced several episodes of nausea and vomiting. He also had lost approximately 15 lb over the past two months. Past history was significant for non-hodgkins lymphoma, which had been in remission for 6 years. During endoscopy, a sessile mucosal lesion with mass effect was visualized in the second part of the duodenum and biopsies were obtained. Pathology was negative for cancer, but did show edema and lymphangiectasia. Endoscopic ultrasound showed a 1 cm cystic lesion in the wall of duodenum at the second portion. A pancreas-preserving duodenectomy was performed. Duodenal specimens showed a cystic lesion in the wall of duodenum. The mucosa overlying the cyst showed a mix of acute and chronic inflammation of the lamiNaPropria. The cyst was located within the muscularis propria, which was hypertrophied. Focal areas showed an epithelial lining composed of columnar/cuboidal cells with basal nuclei and prominent brush border, suggestive of pancreatic ductal epithelium. Based on these findings, a diagnosis of heterotopic pancreas with cystic dystrophy of the duodenal wall was made. Discussion: Duodenal cystic dystrophy due to heterotopic pancreatic deposit is an uncommon pathology. In the past, it was extremely difficult to diagnose without surgery because there are no specific clinical signs. Our case demonstrates effective use of endoscopic ultrasound in precisely locating cysts in the duodenal wall when other imaging modalities, such as CT scan can not. We will present EUS images, histology slides and a detail discussion about heterotopic pancreatic cyst and the role of different diagnostic modalities.