Men are three to four times more likely than women to be diagnosed with bladder cancer. The most common type of bladder cancer is transitional cell carcinoma, comprising 90% of all bladder cancers. Transitional cell carcinomas are staged according to the depth of bladder wall invasion, which also has bearing on treatment options. Superficial transitional cell carcinomas are in the lining of the bladder and have not invaded the deeper bladder muscle wall, whereas muscle invasive cancers have penetrated this layer and are more likely to spread.
Other types of bladder cancer, which are typically less common but more aggressive, include squamous cell carcinomas (2%), which arise due to chronic infection or inflammation, and adenocarcinomas, comprising 1% of bladder cancers and possibly arising from a birth condition known as urachal abnormalities. Finally, small cell carcinomas comprise <1% of bladder cancers, and are typically treated first line with chemotherapy.