Pseudomyxoma peritonei due to mucinous cystadenocarcinoma in situ of the urachus presenting as an inguinal hernia

Pseudomyxoma peritonei is generally caused by appendiceal and ovarian tumors. Other primary sites have been rarely reported. We describe herein the second reported case of pseudomyxoma peritonei due to mucinous cystadenocarcinoma of the urachus. A 54-year-old man was admitted with a left inguinal hernia that had developed several months prior to his admission. During herniorrhaphy, we found a large amount of gelatinous mucinous material in the indirect-hernia sac and made a diagnosis of pseudomyxoma peritonei on cytological grounds. At re-operation, the origin of the pseudomyxoma peritonei proved to be a ruptured urachal cyst. The urachal cyst and the dome of the urinary bladder were excised. In addition, we removed as much of the gelatinous material as possible. On histological examination, a unilocular cyst was found to consist of noninvasive mucinous adenocarcinoma. We succeeded in removing the rest of the mucinous material by postoperative intraperitoneal lavage with dextran solution, and have observed no evidence of recurrence for 7 years since the operation.