A 17-month-old male infant was referred to our hospital, with a complaint of gradually increasing abdominal distension. A huge, tense, fluctuated and smooth mass was palpated occupying most of the abdomen. An abdominal plain film showed a displacement of the intestinal gases to the right, and a CT scanning revealed a cystic mass of water-density below the left lobe of the liver. An aortographic study demonstrated avascular nature of the mass, and displacement of the splenic artery upward and of the aorta to the right side. Laboratory data were all within normal limits. The diagnosis of a mesenteric or pancreatic cyst was made. The child was operated upon. A huge cyst arising from the tail of the pancreas was extirpated completely with a partial resection of the pancreas. No evidence of cystic lesions in the other abdominal organs was present. The cyst measured 16 by 15 by 11 cm and weighed 1,850g. It was unilocular with multiple small cysts in its wall, and contained 1,450ml darkgreen fluid (amylase 189I.U.). The inner surface was roughened by fibrous tag in most part of the main cyst, but was smooth on the walls of the small cysts. Microscopically, much of the epithelial lining of the inner surface was denuded, but partly covered by a single layer of columnar epithelium. There were connective tissue of embryonal nature and sporadic acinar gland and ductal structures of the pancreas, and therefore a diagnosis of congenital pancreatic cyst was made. Congenital pancreatic cysts, especially single cysts of the pancreas are very rare. Ten cases have been reported in the Japanese literature, of which infant cases were only two.
