Cystic mucinous tumors of the urachus: carcinoma in situ or adenoma of unknown malignant potential?

Mucinous cystadenocarcinomas of the urachus are rare. Mucinous benign or premalignant tumors are even rarer, yet pose a challenge in diagnosis and management. We report a case of a 66-year-old man with lower abdominal pain who had a large cystic tumor at the dome of the bladder. En-bloc resection of the tumor with partial cystectomy revealed mucinous cystadenocarcinoma in situ. We reviewed the characteristics of all seven previously reported cases. These tumors are pre-malignant and can cause significant morbidity and mortality. They need to be treated similar to conventional mucinous cystadenocarcinoma by wide surgical resection and partial cystectomy.