Pseudomyxoma Peritonei Arising From a Low-Grade Mucinous Neoplasm of the Urachus

Abstract

Abstract Urachal mucinous tumors range from low-grade lesions traditionally called cystadenomas to frankly invasive mucinous adenocarcinomas. Occasionally, they can lead to the syndrome of pseudomyxoma peritonei (PMP). We report a patient who presented with abdominal distension and had raised tumor markers. A computed tomography scan revealed a calcified cystic lesion of the bladder dome together with features of PMP. These findings were confirmed at laparotomy, and cytoreductive surgery with hyperthermic intraperitoneal chemotherapy was performed. Histologically, the urachal lesion was a low-grade urachal mucinous tumor (mucinous cystic tumor of low malignant potential). The peritoneal disease was associated with ovarian involvement and omental cake and was designated low-grade mucinous carcinoma peritonei on histology. The immunoprofile was typical for lesions of this type, featuring expression of CK20, CEA, and CDX2, but no expression of CK7. We review the literature of PMP arising from urachal primary neoplasms and identify 58 cases reported previously. Based on the limited data available, it appears that urachal lesions account for about 1 in 200 cases of PMP. Owing to the clinical and pathological similarities between urachal and appendiceal mucinous tumors, we recommend a simple classification based on the principles applied to appendiceal lesions and argue this is more appropriate than a classification based on ovarian nomenclature.