Primary mucinous cystadenocarcinoma of the retroperitoneum

Primary retroperitoneal mucinous cystadenocarcinoma (PRMC) is a rare tumour, similar to its ovarian counterpart but without any evidence of ovarian, pancreatic or another extra-retroperitoneal origin. Histogenesis of this neoplasm remains uncertain. Mucinous or coelomic metaplasia of retroperitoneal mesothelium has been recently proposed as its origin. In a 43-year-old woman with a 15-cm cystic lesion in the right retroperitoneum mucinous cystadenocarcinoma was diagnosed, and no primary tumour was identified. Two peritoneal endometriotic foci were found on further surgery. We suggest a common histogenesis for PRMC and these endometriotic foci.