Diagnostic significance of atypical category in the voided urine samples: A retrospective study in a tertiary care center

BACKGROUND: Voided urine samples continue to play an important role in the surveillance of urothelial malignancy and also as a screening mode for high risk patients. In some cases, it is difficult to reliably distinguish changes induced by inflammation, stone or other reactive condition from neoplasm, and these cases are categorized as atypical. The aim of our study is to evaluate the prevalence and the significance of atypical diagnosis in the voided urine samples and also to identify the cytomorphologic features that are seen more frequently in the atypical malignant urine samples. MATERIALS AND METHODS: All voided urine cytology samples with a diagnosis of atypical urothelial cells, between the period of 2000 and 2009, were obtained from the cytology database. Only those cases with histologic follow-up were included in the study. The cytology and the histology slides were retrieved and reviewed. The following parameters were evaluated: cellularity, cell clusters, nuclear membrane irregularities, hyperchromasia and India-ink type nuclei, the presence of spindle cells and the cytoplasmic characteristics. RESULTS: Out of 72 voided urine samples included in the study, 49 cases (68%) had a positive histologic diagnosis of urothelial malignancy in the follow-up histology; of these (55%) were high-grade urothelial carcinoma. Increased cellularity, papillary cell clusters, nuclear membrane irregularity, hyperchromasia and India-ink type nuclei were observed more frequently in the atypical malignant urine samples, while cytoplasmic vacuolization were seen more in the negative reactive urine samples. CONCLUSION: The atypical category diagnosis is associated with a significant proportion of urothelial carcinoma. It should be used by the pathologist to convey concern to the clinician in difficult cases that may require close follow-up.