Mucinous Cystadenoma of the Urachus and Review of Current Classification of Urachal Mucinous Cystic Neoplasms.

Urachal neoplasms are uncommon and represent a minor portion of bladder tumors. According to the recently updated World Health Organization classification (2016), these tumors are classified as adenomas, adenocarcinomas, nonglandular neoplasms, and mixed carcinomas. The mucinous cystic neoplasms represent a small percentage of urachal tumors with morphologic spectrum ranging from benign mucinous cystadenoma to borderline mucinous cystic tumor of low malignant potential and to malignant mucinous cystadenocarcinoma. Benign urachal mucinous cystic adenomas are exceedingly rare, and only a few cases have been reported in the literature to date. The goal of this review is to summarize the clinical features, histopathologic characteristics, treatment, and prognosis of urachal mucinous cystadenoma in light of differentiating them from mucinous cystic tumor of low malignant potential and mucinous cystadenocarcinoma.