How would you treat patients with muscle-invasive urothelial carcinoma of the bladder with small cell and sarcomatoid differentiation?  

Muscle-invasive urothelial carcinoma "with small cell and sarcomatoid differentiation" could represent an inexperienced pathologist failing to recognize a variant of pure urothelial cancer or it might be a stem-cell tumor with variable differentiation. I would start by having the pathology reviewed ...