Clinical and therapeutic significance of aberrant differentiation patterns in bladder cancer.

Pure urothelial carcinoma makes up 90-95% of all bladder cancer. The remaining 5-10% represent urothelial carcinoma with aberrant differentiation patterns and nonurothelial carcinoma. Reviews on this topic often focus on the pathological features of these histologic subtypes. In this review we have summarized the clinical significance of each major histologic pattern and analyzed the response of each to standard treatment modalities. The main limitation to optimizing management is the inability to perform clinical trials owing to the rarity of these tumors. This can be circumvented to some degree by extrapolating knowledge acquired from more common similar tumors in other organ sites. Ultimately, however, multicenter clinical trials will need to be organized to address some key management issues.