Bladder biopsy specimens are usually submitted to rule out a urothelial neoplasm. The procedure may be indicated because of hematuria, an abnormal urine cytology, a history of urothelial neoplasm, or a lesion seen on cystoscopy. About 90% of bladder carcinomas are urothelial, so this will be the focus of this chapter, as well as the unique nomenclature system that is applied to urothelial lesions. Flat neoplasia does not form an exophytic lesion but may still be visible on cystoscopy as a red area. It progresses through dysplasia (rarely diagnosed) to carcinoma in situ. Flat urothelial carcinoma in situ is just known as carcinoma in situ (CIS) and can go on to deeply invasive carcinoma without ever making an exophytic lesion, so always scrutinize the urothelium at high power, especially in denuded areas. Papillary neoplasia has a much wider spectrum of disease, from benign papilloma to high-grade carcinoma. The papillary lesions are unusual in nomenclature; however, in that despite being in situ lesions, they are conventionally just called noninvasive papillary urothelial carcinoma, either low or high grade. If you use the word in situ to refer to papillary lesions, urologists think you mean flat CIS.