[The Paris system for classification of urinary cytology]

A uniform classification system for reporting urinary cytology has not been available until recently, although urinary cytology represents an important volume of specimens in cytopathology laboratories and is well-established in the diagnosis and follow-up of patients with urothelial carcinoma. The Paris system is the first internationally accepted classification system, which allows uniform reporting of urinary cytology based on standardized morphological criteria. It emphasizes the detection of potentially life-threatening high-grade urothelial carcinomas and well-defined diagnostic categories have been developed. Notably, it aims at reducing the diagnosis of equivocal atypia and additionally at confining indications for a rational use of ancillary molecular techniques. The Paris system has already gained broad acceptance both in the cytology and urology communities, and promises to enhance the value of diagnostic urinary cytology.