Adenocarcinoma arising from a gastric duplication cyst.

Malignant transformation in a gastric duplication cyst (GDC) is extremely rare, with only eight reported cases to date. An additional case of an adenocarcinoma arising from a GDC in a 25-year-old male is reported here. Ultrasonography and computed tomography (CT) scans detected a well-defined cyst arising from the greater curvature of the stomach. The patient was submitted to en-bloc resection of the mass with total gastrectomy and regional lymphadenectomy. At the time of laparotomy, the unilocular cyst was full of a thick substance and had no association with the gastric lumen. Microscopic examination revealed that the cystic mass had a well-formed cyst wall with an inner mucosal lining, submucosal layer, muscularis propria, and outer serosal layer. The inner cyst was lined by gastric mucosa. A mediated differentiated adenocarcinoma was found in the duplication cyst, which had invaded the serosa of the cyst wall and the gastric muscular wall. To our knowledge, this is the youngest and only asymptomatic patient in whom neoplastic GDC changes have been reported.