Squamous lesions of the bladder

Squamous lesions of the bladder encompass a broad range of benign and malignant lesions. Many of the squamous lesions restricted to the urothelial surface are generally indolent, such as squamous metaplasia, squamous papilloma and condyloma acuminatum. However, some superficial lesions such as verrucous squamous hyperplasia and squamous cell carcinoma in situ may precede the development of invasive squamous cell carcinoma. Squamous lesions present within the wall of the bladder are often malignant and include classic squamous cell carcinoma and the verrucous squamous cell carcinoma and basaloid squamous cell carcinoma variants. One exception, however, is pseudoepitheliomatous (pseudocarcinomatous) hyperplasia, which is a benign mimicker of invasive squamous cell carcinoma. Our review summarizes the available data on clinical presentation, histopathologic features, differential diagnosis and ancillary tests of the squamous lesions of the bladder.