Introduction: Primary retroperitoneal mucinous cystadenoma (PRMC) and its malignant variant - cystadenocarcinoma are extremely rare tumors known only from case studies and reviews. PRMC is a cystic tumor of the retroperitoneum, which remains asymptomatic for a long time and can reach significant proportions. It occurs mainly in women.
Case report: We present the case of a 38-year-old healthy woman with diagnosed resistance in the right mesogastrium during a c-section. The delivery was terminated without a surgical intervention. The above mentioned resistance was examined further by ultrasound, computed tomography and magnetic resonance imaging. All imaging examinations showed a solid - cystic bilocular expansion, which looked like a mesenteric cyst in the right paracolic area. The patient was asymptomatic at all times, with only a palpable resistance of the abdominal wall. In November 2020, the patient underwent an elective surgery - extirpation of the cystic tumor and prophylactic appendectomy. The operation was performed classically, via midline laparotomy without perioperative perforation of the cystic tumor and without complications in the postoperative period. The histopathological examination showed a malignant variant of PRMC. So far, the patient remains free of any problems and is followed at the department of oncology.
Conclusion: The goal of treatment is to achieve complete surgical removal of the tumor without its perioperative perforation. Due to the rare occurrence of the disease, there are no guidelines for the diagnosis and treatment of PRMC. Precisely because PRMC is a rare tumor, it should be part of the differential diagnosis of cystic tumors of the retroperitoneum, especially when young women are concerned.
Keywords: cystic tumor in pregnancy; mucinous cystadenoma; retroperitoneal tumor.