Urine Cytology

What it does

Urine Cytology reads a scanned liquid-based slide from a voided or instrumented urine sample. It targets high-grade urothelial carcinoma, the lesion that urine cytology is designed to detect, in the haematuria work-up and in bladder cancer surveillance.

The Paris System is built on measurable nuclear features, above all the nuclear-to-cytoplasmic (N/C) ratio, nuclear hyperchromasia, chromatin and nuclear membrane irregularity. The run measures the N/C ratio of each urothelial cell, assigns the specimen to a Paris System 2.0 category and presents the most atypical cells in a gallery, each linked to its position on the slide.

Intended use

Decision support for the cytopathologist and cytotechnologist: a consistent, measured basis for separating negative specimens from atypical ones and suspicious from high-grade. Each category comes with its cell-level evidence.

Who it is for

Cytopathologists, cytotechnologists, general pathologists who sign out urine cytology, and urologists who follow patients under surveillance. Developers use the run to send Paris-coded results with cell measurements to a LIS or a bladder-cancer registry.

Accepted input

• One urine slide per run: a liquid-based preparation of voided urine, catheterised urine or a bladder washing, scanned as a whole-slide image.
• Formats: DICOM VL Whole Slide Microscopy Image or a scanner file (SVS, NDPI, MRXS, iSyntax, SCN, BIF, CZI, OME-TIFF).

Requirements

Requirement	Why
Collection type (voided or instrumented)	Cellularity and expected background differ between the two
Pap stain recorded with the slide	Hyperchromasia and chromatin are judged on Papanicolaou staining
Pixel spacing in µm/px	The N/C ratio is computed from calibrated nuclear and cell areas
Focused cell layer	Nuclear membrane and chromatin features need sharp nuclei

Optional context

Haematuria, a history of urothelial carcinoma, recent instrumentation or intravesical therapy can be passed in clinical_context; the guidance takes them into account.

The result

Section	Content
Paris System category	Adequacy, Paris System 2.0 category, per-cell N/C ratio and a gallery of the most atypical cells
Draft report	Opt-in (options.report): an English narrative that interprets the result for the reader (findings, impression, limitations); every number is checked against the findings

Every cell in the gallery carries its N/C ratio, so the category can be traced to the cells behind it.

Standards

• Reporting: The Paris System for Reporting Urinary Cytology, 2nd edition (TPS 2.0, 2022).
• DICOM: gallery cells as Microscopy Bulk Simple Annotations, the category and N/C measurements in SR TID 1500, an Encapsulated PDF report.
• Interoperability: FHIR R4 DiagnosticReport and Observation, SNOMED CT for the diagnostic category.

Paris System 2.0 categories

Category	What it means for the specimen
Negative for high-grade urothelial carcinoma (NHGUC)	No urothelial cells with significant atypia
Atypical urothelial cells (AUC)	Increased N/C ratio with nuclear atypia short of the suspicious category
Suspicious for high-grade urothelial carcinoma (SHGUC)	Features of high-grade carcinoma in too few cells
High-grade urothelial carcinoma (HGUC)	Enough cells with the full set of high-grade features
Low-grade urothelial neoplasm (LGUN)	Low-grade papillary neoplasia rather than high-grade carcinoma