Morphological Variants of Invasive Urothelial Carcinoma

Urothelial carcinomas exhibit a wide range of morphological variations and various molecular alterations. Many of these variants have significant prognosis and therapeutic implications. The variants/classification has been revised in the 2016 World Health Organization (WHO) classification of tumor of the urinary system and male genital organs. In this chapter, the morphological features, diagnostic criteria and pitfalls, differential diagnoses, immunoprofile, molecular alterations, and clinical and prognostic implications for the common variants of invasive urothelial carcinoma will be reviewed. Rare variants and entities that are not included in the current WHO classification will also be discussed briefly.