A 54-year-old woman presented with a huge palpable mass on left upper quadrant of the abdomen. After preoperative work-up, a cystic disease of pancreatic tail or accessory spleen was initially suspected. We performed exploratory laparotomy and resected both the spleen and a 15 x 11 cm-sized huge cystic mass containing a part of solid component which extended continuously to the pancreatic tail. The solid component, comprising the upper portion of the resected cyst, was reddish brown and granular like as normal splenic tissue. The inner surface of the cyst was smooth and was filled with yellowish white material. Histologic examination showed an epidermoid cyst originating in the accessory spleen of the pancreatic tail lacking hair or skin appendages.