From the Guidelines
The adequacy criteria in The Paris System for Reporting Urinary Cytology require at least 20-30 well-visualized urothelial cells for a specimen to be considered adequate.
Key Points
- Specimens with fewer cells can still be evaluated but should be labeled as "Adequacy Limited" with an explanation of the limitation 1.
- Specimens are considered "Unsatisfactory" when they contain obscuring elements like blood, lubricant, or inflammation that prevent proper assessment of urothelial cells, or when there are technical issues like poor fixation or staining.
- The system acknowledges that cellularity requirements may be lower for instrumented specimens (like catheterized urine) compared to voided urine samples.
- These criteria were established to standardize reporting and ensure reliable cytologic evaluation, as inadequate specimens can lead to false-negative results and missed diagnoses of urothelial carcinoma 1.
Important Considerations
- Proper specimen collection, handling, and processing are essential to meet these adequacy standards.
- The Paris System should be used for reporting urinary cytology, as recommended by the European Society for Medical Oncology (ESMO) 1.
- Urine cytology can facilitate the diagnosis of high-grade urothelial carcinoma but cannot be used as the primary method of histological diagnosis 1.
From the Research
Adequacy Criteria in the Paris System
The Paris System for Reporting Urinary Cytology does not explicitly outline specific adequacy criteria in the provided studies. However, the system focuses on reducing unnecessary indeterminate diagnoses while maintaining its performance in identifying high-grade urothelial carcinoma 2.
Diagnostic Categories
The Paris System comprises seven diagnostic categories:
- Nondiagnostic
- Negative for high-grade urothelial carcinoma (NHGUC)
- Atypical urothelial cells (AUC)
- Suspicious for high-grade urothelial carcinoma (SHGUC)
- High-grade urothelial carcinoma (HGUC)
- Low-grade urothelial neoplasm (LGUN)
- Other malignancies 3
Risk of High-Grade Malignancy
Each category is linked with a specific risk of high-grade malignancy (ROHM), guiding clinical management:
- Nondiagnostic: 17.70% ROHM
- NHGUC: 13.04% ROHM
- AUC: 38.65% ROHM
- SHGUC: 76.89% ROHM
- HGUC and other malignancies: 91.79% ROHM 3
Application of the Paris System
The system has been applied to various studies, including those focusing on upper tract urothelial carcinoma 4 and the evaluation of urine cytology specimens using artificial intelligence 5. However, the adequacy criteria are not explicitly mentioned in these studies.
Urine Cytology Findings
Urine cytology findings in patients with biopsy-confirmed urothelial carcinoma in situ with plasmacytoid features have been evaluated according to the Paris System criteria 6. The study found that the features of this specific type of carcinoma are subtle and often do not meet the Paris System criteria for diagnosis as high-grade urothelial carcinoma.