AMACR-Expressing Urachal Adenocarcinoma 499 FIG. 1. Computed tomography through the lower abdomen showing a midline-lying, well circumscribed multilocular calcified cystic mass (arrow). FIG. 3. The lining tumor cells are stratified columnar epithelium that shows oval to round nuclei and abundant cytoplasm by immunohistochemistry (H&E, x400). FIG. 2. Photomicrograph of the wall of the multilocular cystic mass shows mucin lakes by immunohistochemistry (H&E, x100). FIG. 4. The tumor cells express alpha-methylacyl-coenzyme A racemase by immunohistochemistry (H&E, x400). partial resection of the bladder was performed, including a cuff of the bladder as well. Grossly, the resected bladder margin and inner mucosa were clear without invasion, and we found no evidence of peritoneal implants or pseudomyx- oma peritonei in the intraperitoneal space. 　Microscopically, the tumor was composed of stratified columnar epithelia that lined a cyst. The tumor cells showed oval to round nuclei and abundant cytoplasm (Fig. 2). Mitotic figures were frequently identified. Acellular mucin dissected through the connective tissue mimicking in- vasion, which resulted in diffuse inflammatory responses (Fig. 3). By immunohistochemistry, the tumor cells were positive for cytokeratin 7 (weak), cytokeratin 20, carci- noembryonic antigen (CEA) and AMACR, and negative for prostate-specific antigen (PSA) and high molecular weight cytokeratin (Fig. 4). The final diagnosis was mucinous cys- tadenocarcinoma arising in the urachal remnant of the ab- dominal wall. The patient is alive and well with no evidence of recurrence clinically or radiographically at 12 months af- ter treatment. DISCUSSION Urachal adenocarcinomas are rare, representing less than 0.5% of all bladder cancers and 20-39% of primary adeno- carcinomas of the bladder [1]. Because urachal remnant diseases are uncommon and manifest with nonspecific ab- dominal or urinary signs or symptoms, a definitive presur- gical diagnosis is not easy [7]. Urachal neoplasms follow variable clinical courses. Some cases are associated with early local invasion, so they have a poor prognosis. On the other hand, there are indolent cases of urachal tumours Korean J Urol 2010;51:498-500