Analysis of the Cytomorphological Features in Atypical Urine Specimens following Application of The Paris System for Reporting Urinary Cytology.

Background: This study investigates the use of The Paris System (TPS) for Reporting Urinary Cytopathology and examines the performance of individual and combined morphological features in atypical urine cytologies.

Methods: We reviewed 118 atypical cytologies with subsequent bladder biopsies for the presence of several morphological features and reclassified them into Paris System categories. The sensitivity and specificity of individual and combined features were calculated along with the risk of malignancy.

Results: An elevated nuclear-to-cytoplasmic ratio was only predictive of malignancy if seen in single cells, while irregular nuclear borders, hyperchromasia, and coarse granular chromatin were predictive in single cells and in groups. Identification of coarse chromatin alone yielded a malignancy risk comparable to 2-feature combinations. The use of TPS criteria identified the specimens at a higher risk of malignancy.

Conclusion: Our findings support the use of TPS criteria, suggesting that the presence of coarse chromatin is more specific than other individual features, and confirming that cytologic atypia is more worrisome in single cells than in groups.