Though there are other rare forms, the three chief types of bladder cancer are Urothelial carcinoma, Squamous cell carcinoma, and Adenocarcinoma. Urothelial carcinoma is by far the most common, accounting for nearly 90% of bladder cancer cases. Squamous cell carcinomas result from long-term irritation to the cells of the bladder and account for 4% of cases, while 2% of bladder cancers are classified as Adenocarcinoma which develops from glandular cells. Bladder cancer is also classified by other terms as well, with noninvasive cancer describing the disease which has not spread and is easily removed. Non-muscle invasive and invasive types describe varying degrees of growth and, therefore, seriousness.