The Paris System: achievement of a standardized diagnostic reporting system for urine cytology

Utility of the Paris System in Urine Cytology for Improved Screening of High-Grade Urothelial Carcinoma in Bahrain

BACKGROUND

Urothelial carcinoma, a prevalent and aggressive urological malignancy, necessitates early detection for improved prognosis. Urine cytology serves as a cost-effective screening tool, but inconsistencies in reporting due to the lack of standardized criteria limit its efficacy. The Paris System for reporting urinary cytology (TPS) was introduced to address this issue, aiming to improve diagnostic accuracy. This retrospective study investigates the effectiveness of urine cytology in detecting high-grade urothelial carcinoma (HGUC) using TPS classification, specifically focusing on atypical urothelial cells (AUC) categorized as TPS-III and suspicious for high-grade urothelial carcinoma (SHGUC) categorized as TPS-IV.

METHODS

We reviewed 470 urine cytology samples collected over two years at a tertiary healthcare center in Bahrain. All samples were re-evaluated using TPS classification by two independent consultant cytopathologists blinded to the original cytology report. The analysis included only samples categorized as TPS-III or TPS-IV with corresponding histopathology reports from confirmatory biopsies performed within four months of urine collection. Biopsy results were categorized as either benign/low-grade urothelial carcinoma (non-HGUC) or malignant (HGUC). The positive predictive value (PPV) of urine cytology for HGUC detection was calculated for both TPS-III and TPS-IV categories. Statistical significance was assessed using Fisher's exact test.

RESULTS

Among the 470 urine cytology samples, 40 (8.5%) were classified as TPS-III or TPS-IV. Within this subset, 16 patients underwent confirmatory biopsies. Histopathological analysis revealed HGUC in 12 (75%) patients and non-HGUC (benign or low-grade) in 4 (25%) patients. The PPV of TPS-III for HGUC was 50%, while TPS-IV demonstrated a higher PPV of 90%. However, the difference between these values was not statistically significant (p = 0.25). This study explored the utility of TPS classification in urine cytology for HGUC detection. While SHGUC (TPS-IV) exhibited a numerically higher PPV compared to AUC (TPS-III), the lack of statistical significance necessitates further investigation. Our findings highlight the potential of TPS to improve the accuracy of urine cytology. TPS implementation has been shown to reduce the number of inconclusive "atypical" diagnoses, leading to more targeted investigations.

CONCLUSION

Our study suggests that SHGUC (TPS-IV) within TPS classification framework might hold promise as a more specific indicator for HGUC compared to AUC (TPS-III). However, further research with larger cohorts is necessary to definitively establish the clinical significance of this observation. This investigation paves the way for future studies exploring the potential of TPS, particularly the SHGUC category, as a reliable screening tool for HGUC, potentially leading to earlier diagnoses and improved patient outcomes.

Digital image analysis of high-grade urothelial carcinoma in urine cytology confirms chromasia heterogeneity and reveals a subset with hypochromatic nuclei and another with extremely dark or "India ink" nuclei

BACKGROUND

The Paris System for Reporting Urinary Cytology (TPS) uses hyperchromasia as major diagnostic criterion for high-grade urothelial carcinoma (HGUC). The purpose of the study was to evaluate cases that were diagnosed as HGUC by TPS and determine whether there are different chromatin distribution patterns (ie, subsets).

METHODS

Digital image annotations were performed on microscopic images of HGUC urine specimens with surgical biopsy/resection follow-up. Median gray values were generated for each cell. Neutrophils (polymorphonuclear leukocyte [PMN]) were also enumerated in each case to serve as an internal control. A HGUC/PMN ratio was generated for each case, and the cases were distributed.

RESULTS

Sixty-nine HGUC cases yielded 2660 cells, including 2078 HGUC (30.1 cells/case) and 582 PMNs (8.4 cells/case). The average median gray value of an HGUC was 50.6 and of a PMN was 36.8 (P < .0001). Eight of 69 cases (11.6%) contained nuclei that, on average, were darker than or as dark as a PMN (extremely dark, ie, "India ink"). Fifty-one of 69 cases (74.0%) contained nuclei that, on average, were slightly brighter than a PMN (hyperchromatic). Ten of 69 cases (14.5%) contained nuclei that, on average, were much brighter than a PMN (hypochromatic). Within a single case, all cases showed heterogeneity with the hypochromatic cases showing the most dramatic effect.

CONCLUSIONS

Digital image analysis reveals that there are large variations in chromasia between cases including a subset of cases with hypochromasia and another with extremely dark or "India ink" nuclei. There was much heterogeneity of chromasia seen within a single sample.

Should "suspicious for high-grade urothelial carcinoma" and "positive for high-grade urothelial carcinoma" remain separate categories?

BACKGROUND

The Paris System (TPS) for Reporting Urinary Cytology aims to standardize urine cytology reporting. Per TPS, the diagnosis of "suspicious for high-grade urothelial carcinoma (SHGUC)" is applied in cases that have few urothelial cells with severe atypia but are quantitatively insufficient for a diagnosis of "high-grade urothelial carcinoma (HGUC)." In our study, we compared the diagnostic accuracy and risk of malignancy (ROM) of these 2 categories to assess whether they could be combined in clinical practice to perhaps improve overall interobserver variability.

METHODS

All urine specimens with a diagnosis of either SHGUC or HGUC from January 2016 to July 2019 were retrieved from the pathology database of 2 large academic institutions. Only cases with follow-up biopsies within 6 months were included.

RESULTS

One hundred eighty-nine cases met the study criteria. Of these, 122 had a cytologic diagnosis of SHGUC, and 67 had a diagnosis of HGUC. Ninety-five (78%) cases from the SHGUC group and 64 (96%) cases from the HGUC group had biopsy-proven HGUC. The majority of cases with discordance had a history of treatment with either intravesical bacillus Calmette-Guérin or mitomycin. The difference in the rate of biopsy-proven HGUC between the SHGUC category and the HGUC category (95/122 vs 64/67, respectively) was statistically significant (P < .001).

CONCLUSIONS

The difference in ROM between SHGUC and HGUC was statistically significant in our study cohort. Intravesical chemotherapy was frequently observed in negative biopsy cases in both groups. Our preliminary findings suggest that the 2 TPS categories should remain separate.

The Paris System for Reporting Urinary Cytology reduces atypia rates and does not alter the negative predictive value of urine cytology

INTRODUCTION

The Paris System for Reporting Urinary Cytology (TPS) was developed for standardization purposes and it placed an emphasis on screening for high-grade urothelial carcinoma (HGUC). Since then, it has shown to reduce atypia rates and better correlate with surgical specimens. The aim of this study was to calculate the negative predictive value (NPV) of urinary cytology for detecting HGUC using TPS and compare these data to our recently published pre-TPS cohort. As a screening test, it is imperative that TPS has a high NPV.

MATERIAL AND METHODS

A search of our institution's pathology database for the term "negative for HGUC" from January 1, 2016, to December 31, 2017, was conducted. A true negative was defined as a patient with at least 1 subsequent negative urine cytology/surgical biopsy specimen or the patient being clinically negative for 6 months. NPV rates were calculated based on the data obtained.

RESULTS

The cohort consisted of 2960 urine cytology specimens from 1894 patients. A total of 99 false negatives were identified, generating a NPV of 96.7% (2861/2960). This NPV is identical to our previously published pre-TPS cohort (years 2012-2013; NPV: 96.7%). The clinical indication most effected NPV, with a history of urothelial carcinoma with a NPV of 93.9% followed by hematuria at 98.9%. The atypia rate in years 2012-2013 was 8.2% and in 2016-2017 it was 5.7% (P < 0.001).

CONCLUSIONS

We demonstrate that TPS did not alter the NPV for detecting HGUC compared to our pre-TPS cohort. We believe that TPS is an effective reporting system for screening HGUC in urinary cytology.