Mucinous cystic tumors of low malignant potential (MCTLMP) are rare urachal neoplasms. The morphological characteristics and clinical prognosis of MCTLMP is similar to that of mucinous cystic tumors occurring in the ovary and appendix. After complete resection, almost no cases of recurrence or metastasis have been reported. Because MCTLMP is rare, it may be missed in the clinic. MCTLMP can lead to the formation of pseudomyxoma peritonei (PMP), which manifests as the widespread production of mucus in the abdominal cavity and makes the disease complex or difficult to diagnose. At present, only 3 cases of MCTLMP with PMP have been reported in the literature. In the present study a fourth case of urachal MCTLMP in a 74-year-old male that resulted in widespread PMP is presented. Initially, a multilocular cystic lesion was revealed in the urachal duct area at the anterior upper margin of the bladder after a patient, experiencing lower abdominal pain, was imaged. As revealed using light microscopy, the cyst was lined with a mucous columnar epithelium, and part of the epithelium indicated pseudolamellar hyperplasia and papillary structures. The cells indicated mild atypia and low mitotic activity. There was no stromal infiltration of tumor cells, and a large amount of mucous exudate was observed. As preoperative computed tomography examination suggested the presence of a large amount of ascites and there were increased levels of blood tumor markers, carcinoembryonic antigen and carbohydrate antigen 125, clinicians considered that the diagnosis maybe a malignant tumor of the urachal gland with peripheral dissemination. However, the diagnosis of MCTLMP with PMP was confirmed by histopathological examination. The mass was completely removed, along with part of the peritoneum and bladder wall as these were within the tumor margin. The appendix appeared normal during surgery. A one off dose of intraperitoneal infusion chemotherapy with 1,000 mg 5-fluorouracil was performed after surgery. No recurrence was observed during the 8-month follow-up period.
Keywords: ascites; mucinous cystic tumor of low malignant potential; mucus; pseudomyxoma peritonei; urachus.
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