Urothelial Dysplasia and Its Mimics

Nonpapillary (flat) intraepithelial lesions of the urothelium include reactive epithelial abnormalities as well as preneoplastic (dysplasia or low-grade intraurothelial neoplasia) and neoplastic noninvasive (carcinoma in situ or high-grade intraurothelial neoplasia) lesions.