Primary retroperitoneal tumor: mucinous cystoadenocarcinoma.

Primary retroperitoneal mucinous cystadenocarcinomas (PRMCs) are extremely rare tumors with limited understanding of their pathogenesis and biological behavior. We describe a case of a 50-year-old female patient who underwent surgical treatment. The patient had a history of previous surgeries for mesenteric mucinous cystadenoma, without evidence of recurrence. During routine abdominal ultrasound a new tumor was found. An abdomen magnetic resonance imaging was done and confirmed the presence of a cystic lesion in the right iliac fossa. After discussion in multidisciplinary committee, surgical complete resection of the tumor, along with bilateral adnexectomy, was performed successfully. Histopathological examination revealed a mucinous adenocarcinoma adjacent to a mucinous cystadenoma. Immunohistochemical analysis supported the diagnosis of a primary retroperitoneal lesion. The patient had an uneventful recovery and has remained disease-free during the two-year postoperative follow-up. PRMCs are challenging to diagnose preoperatively due to nonspecific symptoms. Surgical excision is the mainstay of treatment. The long-term prognosis and optimal therapeutic strategies require further investigation.