Ectopic Pancreas with Walled-off Necrosis Mimicking Malignant Submucosal Gastric Tumor

An ectopic pancreas rarely transforms into a malignancy, and the symptoms vary from patient to patient. The most commonly observed site of an ectopic pancreas is the antrum of the stomach. A 59-year-old male patient with severe abdominal pain underwent CT. A 9.6 cm-sized well-defined exophytic huge mass with heterogenic density was located between the stomach distal antrum and duodenum. A malignant submucosal tumor was suspected because of the exophytic dirty huge mass. Initially, surgery was considered to confirm the histological evaluation. After 2 months, the abdominal pain disappeared, and the follow-up MRI scan showed a decrease in size, which contained a necrotic component inside. It was confirmed that the parenchymal tissue was the pancreas. The pathology through EUS-guided fine needle aspiration (EUS-FNA) was normal pancreatic acinar cells, smooth muscle fragments, squamous cyst, and some neutrophils (abscess). Walled-off necrosis occurs as a complication of acute pancreatitis with parenchymal tissues and surrounding tissues, but complications of ectopic pancreatitis occurred in this case. Abdominal pain due to ectopic pancreas leading to the formation of a giant abscess has been reported as a very rare case. Diagnosis through biopsy is most important when a malignant submucosal tumor is suspected. In addition, it is important to determine the clinical features, examination findings, such as EUS, CT, and MRI, and the changes according to the follow-up period. This paper reports a case of ectopic pancreas, resulting in necrotic tissue and walled-off necrosis, abdominal pain, and spontaneous improvement.