'The ultimate goal is to relate the tumor genotype with the individual's phenotype and to offer patients treatment that is adapted to the specific molecular pattern of their cancer.'The urothelium is the epithelium that lines the upper and lower urinary tract. Over 95% of urothelial carcinomas are derived from the urothelium [1,2]. They can be located in the lower tract (bladder or urethra) or upper tract (pyelocaliceal cavities or ureter). Urothelial carcinomas are the fourth most common tumors after prostate (or breast) cancer, lung cancer and colorectal cancer. Bladder tumors account for 90-95% of urothelial carcinomas, and it is the most common malignancy of the urinary tract and the second most common malignancy of the urogenital tract after prostate cancer. It accounts for 5-10% of all cancers diagnosed each year in Europe [1,2]. Bladder cancer is ranked the 11th most common cancer in the world and over 50% of cases occur in developed countries [1,2]. Conversely, upper urinary tract transitional cell carcinomas (UUT-TCCs) are scarce and account for only 5-10% of urothelial carcinomas [2,3]. The estimated annual incidence in Western countries is approximately one to two new cases per 100,000 inhabitants.'Bladder cancer is ranked the 11th most common cancer in the world and over 50% of cases occur in developed countries.'Pyelocaliceal tumors are approximately twice as common as ureteral tumors. In 8-13% of cases, a synchronous bladder cancer is present. Recurrence in the bladder or the contralateral urinary tract occurs in 30-51% of UUTTCCs. The natural history of UUT-TCCs differs from that of bladder cancer: 60% of UUTTCCs are invasive at diagnosis compared with only 15% of bladder tumors. Moreover, UUTTCCs invading the muscle wall usually have a very poor prognosis. The 5-year specific survival is less than 50% for pT2/pT3 and less than 10% for pT4 [3,4]. Although the mechanisms of carcinogenesis are thought to be similar throughout the urinary tract, recent epidemiological data and genetic studies suggest otherwise. It is now obvious that strong differences exist with regard to tumor location and behavior between the upper and the lower urinary tract.