Subtitle: The Paris System for Reporting Urinary Cytology 2.0 (2022): the six categories, adequacy, the HGUC, SHGUC and AUC criteria, why low-grade neoplasms are reported as negative, risk of high-grade malignancy, common mimics (polyomavirus, instrumentation, treatment effect, stones) and ancillary testing, with 8 MCQs for NEET-SS, DM, FRCPath and fellowship exams.
Author: PathologyMCQ Editorial Board
Category: Cytopathology
Last Updated: October 2026
Read Time: 7 minutes
At-a-Glance
- TPS reports urine cytology around one question: is high-grade urothelial carcinoma present?
- Six categories: nondiagnostic, NHGUC, AUC, SHGUC, HGUC, other malignancies.
- HGUC: at least 5 cells with N:C 0.7 or more, hyperchromasia, and coarse chromatin or irregular membranes. SHGUC: fewer than 5 such cells.
- AUC: N:C 0.5 or more plus one other nuclear abnormality.
- Low-grade urothelial neoplasm is reported as negative unless fibrovascular cores are seen.
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Why The Paris System
Before 2016 urine cytology was reported with inconsistent terminology and a large, unhelpful atypical group. The Paris System (TPS, 2016; second edition 2022) standardised reporting by accepting that cytology is sensitive and specific for high-grade urothelial carcinoma but poor at detecting low-grade papillary lesions, which are best found cystoscopically. Every category is therefore defined by its relationship to HGUC.
Adequacy
- Voided urine: at least 30 mL is recommended; smaller volumes are acceptable if cellular. Fewer than 10 well-preserved urothelial cells per 10 high-power fields is considered low cellularity, and a specimen can be reported as nondiagnostic if it is obscured, degenerated or scant.
- Instrumented urine (catheterised, washing): a minimum of about 20 well-preserved urothelial cells per 10 high-power fields.
- Any specimen with cells that are atypical or worse is adequate by definition.
- State the specimen type (voided, catheterised, washing, upper tract, ileal conduit) because background and cellularity differ.
The Six Categories
The Paris System 2.0 categories
| Category | Definition | Typical report |
|---|---|---|
| Nondiagnostic / unsatisfactory | Scant, degenerated or obscured, with no atypical cells | Repeat |
| Negative for HGUC (NHGUC) | Benign urothelial, squamous and glandular cells; reactive and treatment changes; includes LGUN without fibrovascular cores | Routine follow-up |
| Atypical urothelial cells (AUC) | N:C 0.5 or more plus hyperchromasia, coarse chromatin or irregular membranes; falls short of SHGUC | Correlate with cystoscopy; consider repeat or FISH |
| Suspicious for HGUC (SHGUC) | Fewer than 5 cells meeting all HGUC criteria | Cystoscopy and biopsy |
| High-grade urothelial carcinoma (HGUC) | At least 5 cells with N:C 0.7 or more, hyperchromasia, and coarse chromatin or irregular membranes | Cystoscopy, biopsy, upper tract imaging |
| Other malignancies | Primary non-urothelial (squamous, adenocarcinoma, small cell) and secondary tumours (prostate, colorectal, cervix, renal, melanoma, lymphoma) | Name the tumour; immunocytochemistry on cell block |
Criteria in Detail
Cytological criteria
| Feature | HGUC | SHGUC | AUC |
|---|---|---|---|
| N:C ratio | 0.7 or more | 0.7 or more | 0.5 or more (mandatory) |
| Hyperchromasia | Present | Present | One of hyperchromasia, coarse chromatin or irregular membranes |
| Chromatin | Coarse, clumped (one of these two required) | Same | See above |
| Nuclear membrane | Markedly irregular (one of these two required) | Same | See above |
| Number of cells | At least 5 | Fewer than 5 | Any |
- Judge the N:C ratio on the area of the nucleus relative to the whole cell, not the diameter; degenerated cells with lost cytoplasm are a trap.
- HGUC cells are often single, with eccentric nuclei, dense cytoplasm and a dirty necrotic background; three-dimensional clusters raise the possibility of a papillary tumour but do not grade it.
- Low-grade urothelial neoplasm: papillary fragments with bland nuclei; only when a true fibrovascular core is present can LGUN be mentioned, and the specimen still falls under NHGUC.
Risk of High-Grade Malignancy
Approximate risk of high-grade malignancy (ROHM)
| Category | ROHM |
|---|---|
| Nondiagnostic | Variable; similar to NHGUC if truly scant |
| NHGUC | About 5–10% |
| AUC | About 10–35% |
| SHGUC | About 50–90% |
| HGUC | About 90% or more |
Mimics and Pitfalls
Common mimics of HGUC
| Mimic | Clue |
|---|---|
| Polyomavirus (BK) decoy cells | Single homogeneous ground-glass inclusion, smudged chromatin, smooth membrane; SV40 positive |
| Instrumentation | Cohesive papillary-like clusters of bland cells with umbrella cells; uniform chromatin |
| Urolithiasis | Papillary clusters, reactive atypia, crystals and inflammation |
| BCG, mitomycin, thiotepa | Nuclear enlargement with preserved N:C ratio, vacuolation, multinucleation, granulomatous background |
| Radiation | Cytomegaly with proportionate nucleomegaly, polychromasia, vacuoles |
| Degeneration | Pyknotic nuclei, loss of cytoplasm giving a falsely high N:C ratio |
| Seminal vesicle cells | Golden-brown lipofuscin, degenerate dark nuclei, sperm in background |
| Renal tubular cells | Small, degenerated, round, often in casts; upper tract specimens |
Ancillary Tests
- UroVysion FISH: gains of chromosomes 3, 7 and 17 and loss of 9p21 (CDKN2A); useful for AUC, SHGUC and surveillance after BCG.
- Cell block immunocytochemistry: GATA3, p63, CK5/6 and uroplakin II for urothelial origin; PSA/NKX3.1 for prostate; CDX2 for colorectal; TTF1 and synaptophysin for small cell carcinoma.
- SV40 immunostain for polyomavirus when decoy cells are suspected.
- Urine-based molecular assays (FGFR3, TERT promoter, methylation panels) are emerging adjuncts, not replacements for cystoscopy.
Test Yourself: 8 MCQs
The Paris System: 8 MCQs
Categories, HGUC and SHGUC criteria, AUC, LGUN, mimics and ancillary tests, with instant explanations.
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Exam Pearls
- Count the cells: 5 or more = HGUC, fewer than 5 = SHGUC.
- N:C 0.7 for HGUC and SHGUC; 0.5 for AUC.
- LGUN is negative for HGUC unless fibrovascular cores are present.
- Decoy cells and treatment effect are the classic false positives; degenerated cells inflate the N:C ratio.
- UroVysion: 3, 7, 17 gains and 9p21 loss.
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References
- Wojcik EM, Kurtycz DFI, Rosenthal DL, eds. The Paris System for Reporting Urinary Cytology. 2nd ed. Springer; 2022.
- Barkan GA, et al. The Paris System for Reporting Urinary Cytology: the quest to develop a standardized terminology. Acta Cytol. 2016;60:185–97.
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