Histologic variants of infiltrating urothelial carcinoma

Context. - The spectrum of urothelial carcinoma is broad, and variant morphologies are being reported continually. Many of these variants have been extensively documented and even established as subclasses of urothelial carcinoma. Objective. - To review the established and more recently described variants of urothelial carcinoma. The significance of recognizing these variants is discussed. Data Sources. - The literature is reviewed in conjunction with our experience pertaining to urothelial carcinomas of the bladder and ureters. Conclusions. - Urothelial carcinoma displays many forms, and some of these variant morphologies may introduce diagnostic difficulties because of their similarity to other malignancies and/or benign lesions. Additionally, it is important to recognize variants that are associated with different outcomes from conventional urothelial carcinoma. For these reasons, familiarity with the diverse morphology of urothelial carcinoma is not simply an academic exercise but is important in providing quality care for patients affected by this disease.