[Giant retroperitoneal cystic mass: appendiceal mucocele]

Appendiceal mucocele is a term used to describe the dilatation of the vermiform appendix produced by an intraluminal accumulation of mucus. Four pathological processes have been described that may lead to an appendiceal mucocele: obturation of cecoappendiceal communication, mucosal hyperplasia, mucinous cystadenoma and mucinous cystoadenocarcinoma. The most frequent is mucinous cystadenoma, seen in 50% of appendiceal mucoceles. 6% of patients with appendiceal mucocele develop peritoneal pseudomixoma, possibly through dissemination of the epithelial cells into the abdominal cavity. Preoperative diagnosis of the lesion is particularly important in order to deal with it carefully during surgery. CT scan is the most precise radiological exploration, although there are no pathognomonic signs of mucocele. Typical CT finding of a mucocele is a well-defined cystic mass that compresses the cecum without any peripheral inflammatory reaction, and with low levels of attenuation that vary between water and soft tissue density. We present a case of an appendiceal mucocele caused by a mucinous cystadenoma clinically presented as a giant retroperitoneal mass. Diagnosis was postoperatively made, after pathological study of the surgical sample.