Abstract
Bladder tumors can be broadly divided into those of epithelial or mesodermal origin. Furthermore, 90% of bladder tumors arise from the epithelium of the bladder, and most cases of bladder cancer are histologically urothelial carcinomas. Mesodermal tumors are exceptionally rare and often benign. Of the mesenchymal tumors of the bladder, leiomyomas are the most common, and their prognosis depends on their histology. The present report describes a case of submucosal urothelial cancer in a patient with no past history of bladder cancer. To the best of our knowledge, there are no previous reports of urothelial cancer occurring in the submucosa. The present report was the first to document a case of submucosal urothelial cancer, whose diagnosis was made possible only by transurethral resection of bladder tumor. Although the precise pathomechanism of the present case was unclear, two hypotheses were considered. First, the urothelial cancer developed within a diverticulum, then the entrance of the diverticulum closed, sealing in the cancer. Second, the bladder cancer stemmed from aberrant urothelium in the submucosal tissue. If submucosal urothelial bladder carcinoma develops within the diverticular environment, its prognosis can be as poor as that of invasive bladder cancer due to the features of the diverticular environment. Even in a patient with a submucosal bladder tumor but no previous history of bladder cancer, bladder cancer should be considered in the differential diagnosis.