Intrapancreatic gastric duplication cyst mimicking pancreatic cystic tumor.

Cystic lesions of the pancreas are sometimes difficult to diagnose. We report a case of a gastric duplication cyst (GDC) of the pancreas in an adult. A 45-year-old woman was admitted to our department for the investigation of anemia. Abdominal ultrasonography revealed a large cystic lesion, measuring about 40 × 70 mm with calcification in the tail of the pancreas. Contrast-enhanced computed tomography of the abdomen revealed a non-enhanced cystic lesion with non-enhanced wall. Endoscopic retrograde pancreatography revealed a mild extended main pancreatic duct and an aberrant pancreatic duct, but there was no communication with the cyst. We could not deny the malignancy, so distal pancreatectomy was performed. The pathological examination revealed that the inner wall of the cyst consisted of columnar epithelium and smooth muscle layer. Immunohistochemical analysis revealed the columnar epithelium to be immunopositive for cytokeratin 7 (CK7) and immunonegative for cytokeratin 20 (CK20) and the glands to be immunonegative for CK 7 and immunopositive for CK 20. Therefore, a diagnosis of GDC of the pancreas was made. On imaging, a GDC usually mimics a pancreatic pseudocyst or a cystic neoplasm of the pancreas. Therefore, even though it is rare, a GDC should be considered in the differential diagnosis of cystic tumors of the pancreas.