RESEARCH ARTICLE n

Full list of author information is available at the end of the articleand is characterized by frequent mutations in TP53, RB and PTEN [1]. Morphologically, UCa consists of invasive nests of carcinoma cells with variable atypia and fre-quent surrounding retraction artifact (Figure 1A), al-though this appearance can vary significantly. Less fined as pure morphologic entities that lack a typical urothelial component [2]. Our understanding of the mo-lecular relationships between these other forms of blad-der cancer that arise from the urothelial lining has been limited and may be based on the low number of cases available for study and/or lack of significant attention paid to this topic. It appears, however, that despite a * Correspondence: dhansel@ucsd.edu1Department of Pathology, University of California at San Diego, 9500 GilmanUrothelial carcinoma (UCa) represents the most com-Background: Bladder cancer exists as several distinct subtypes, including urothelial carcinoma (UCa), squamous cell carcinoma (SCCa), adenocarcinoma and small cell carcinoma. These entities, despite showing distinct morphology and clinical behavior, arise from the urothelial lining and are often accompanied by similar precursor/in situ findings. The relationship between these subtypes has not been explored in detail