Primary retroperitoneal mucinous cystadenocarcinomas are a distinct entity.

Primary retroperitoneal mucinous cystadenocarcinomas are rare tumors with a controversial pathogenesis. Present report describes a 74-year-old woman with a retroperitoneal cystic pelvic mass. Her past medical history included appendectomy, bilateral salpingo-oophorectomy, and a hysterectomy. An explorative laparotomy was performed and the mass was completely excised. Definitive pathology revealed a primary retroperitoneal mucinous cystadenocarcinoma of the ovarian type. Further management consisted of four cycles carboplatin. She had a recurrence after 8 months and died 31 months after the initial diagnosis. Primary retroperitoneal mucinous cystadenocarcinomas are distinct entity, with the same poor prognosis as their ovarian counterpart.