Multiprobe fluorescence in situ hybridization (UroVysion) for the detection of urothelial carcinoma - FISHing for the right catch

Urinary cytology has a well-established role in the detection and monitoring of urothelial carcinoma. The main strength of cytology is the high specificity for high-grade urothelial carcinoma and carcinoma in situ, but it has a low sensitivity for low-grade, non-invasive tumors. There are several other limitations of cytology. Cytology of the upper urinary tract and after intravesical therapy with bacillus Calmette-Guerin is notoriously difficult to interpret. In addition, there is a poorly defined but commonly used category of atypical cytology of uncertain significance. The UroVysion multiprobe fluorescence in situ hybridization has emerged as a helpful tool to address these limitations. It consists of fluorescently labeled DNA probes to detect increased copy numbers (polysomy) of the chromosomes 3, 7 and 17 and deletion of 9p21, the site of the P16 tumor suppressor gene. Multiple studies have shown that fluorescence in situ hybridization in voided urine and washing specimens can help in patient management due to its superior sensitivity over cytology in different situations. It can be particularly useful to clarify equivocal cytological findings. However, some aspects remain to be further addressed including cost efficiency, optimal cut-off values and the true performance under real-life conditions.