We report on a 79-year-old woman patient with a tumor with a diameter of 18 cm in the right flank. The medical history of the patient was normal except for a single asymptomatic gallstone, which had been known since 12 years. Sonography and abdominal CT showed an enormous intra-abdominal mass filled with liquid with a permanent union with the gallbladder. We than performed an explorative laparotomy with a tumor resection and a cholecystectomy. The histological examination showed perforation of the gallbladder with a great pseudocyst filled with 1800 ml infected bile and with penetration through the abdominal wall.