A 15-YEAR-OLD white girl presented with a history of acute, left upper quadrant abdominal pain that developed while she was performing gymnastics. She had no history of trauma or pancreatitis. An abdominal computed tomographic scan revealed a large mass in the tail of the pancreas. The differential diagnosis based on the computed tomographic scan included pancreatic pseudocyst and papillary cystadenoma. An endoscopic retrograde cholangiogram and pancreatogram showed a J-shaped stomach consistent with extrinsic compression, an inferiorly displaced main pancreatic duct with a smooth, tapered narrowing, and no filling of the pancreatic tail. There was no evidence of communication of the pancreatic duct with the mass. The cholangiogram showed no abnormalities. Exploratory laparotomy showed a large mass involving the pancreatic tail and adherent to the splenic artery and vein. A distal pancreatectomy and splenectomy was performed; the gross specimen showed an 11-cm-diameter mass that markedly distended the pancreatic tail (Figure 1). On cut section, the mass had a multicystic, hemorrhagic, and necrotic appearance (Figure 2). The tissue was examined histopathologically (Figure 3).