Recently described and unusual variants of urothelial carcinoma of the urinary bladder

Urothelial carcinoma (UC) of the urinary bladder has a great propensity to undergo divergent differentiation. The resulting subtypes are morphologically unique and have significant prognostic and therapeutic differences. While squamous and glandular subtypes are the most common, a number of other well characterised morphological subtypes were described in the 2004 World Health Organization Classification. More recently additional variants of UC have been described, while others have been more fully characterised. In this review we report the details of recently described and selected unusual variants of UC. Specifically, the pathological and clinical details are discussed, relating to large nested and nested variant of UC, large cell undifferentiated carcinoma, lymphoepithelioma-like carcinoma, osteoclast rich undifferentiated carcinoma, pleomorphic giant cell carcinoma, UC with syncytiotrophoblastic giant cells, lipid cell variant of UC, micropapillary UC, UC with abundant myxoid stroma and plasmacytoid UC.