The scientific name for bladder cancer is "urothelial carcinoma," formerly known as "transitional cell carcinoma." Urothelial carcinoma is the most common type of bladder cancer, accounting for the majority of cases. It originates in the urothelial cells, which line the inside of the bladder and the urinary tract. Other less common types of bladder cancer include squamous cell carcinoma, adenocarcinoma, and small cell carcinoma, but urothelial carcinoma is the most prevalent.