A fundal cyst of the gallbladder: An unusual abdominal mass.

A female, aged 80 years, presenting with a large abdominal mass causing distension and right-sided hydronephrosis, is presented. The mass proved to be a unilocular cyst attached to the fundus of a thick-walled gallbladder. Histological examination demonstrated invasive adenocarcinoma in the gallbladder. The cyst was lined by gallbladder type epithelium which showed the appearances of carcinoma-in-situ. The aetiology of this cystic lesion is discussed. It seems most likely that it is an acquired lesion caused by occlusion of the communication into a fundal diverticulum. This lesion is unusual, but should be considered in the differential diagnosis of obscure intraabdominal masses.