Challenges in the Diagnosis of Urothelial Carcinoma Variants: Can Emerging Molecular Data Complement Pathology Review?

Urothelial carcinoma can exhibit a wide variety of histopathologic phenotypes or variant morphologies, classifications of which have recently been revised in the 2016 World Health Organization Classification of Tumours of the Urinary System and Male Genital Organs . Many of these variants not only present diagnostic challenges, but also have clinical implications that affect patient prognosis and treatment strategies. This review will discuss these variant morphologies and their relationship to current understanding of the underlying biology of urothelial carcinoma and molecular classification paradigms.