Bladder cancer monitoring

Paris System for Urine Cytology — What Each Category Means

A urine cytology report using the Paris System assigns your sample to one of six categories. Each reflects how the cells look under the microscope and what level of concern that raises. The category is one piece of information — not a diagnosis on its own.

Medically reviewed by Dr. Muralidhar Muddusetty, Surgical Oncologist, MBBS (AIIMS) · MS Surgery (AIIMS) · DNB Surg Onc · MRCS (Edinburgh) · Last reviewed September 2026

Six standard categories — The Paris System uses consistent terminology so any specialist reading your report understands the finding in the same way.
Built around high-grade disease — The system is designed specifically to detect high-grade urothelial carcinoma, the most dangerous form.
Not a diagnosis on its own — Your category is read alongside cystoscopy results, imaging, and your clinical history — never in isolation.
Atypical is a middle category — Atypical Urothelial Cells sits between Negative and Suspicious, and it almost always requires follow-up.

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The Paris System divides urine cytology into six categories: Nondiagnostic, Negative for High-Grade Urothelial Carcinoma, Atypical Urothelial Cells, Low-Grade Urothelial Neoplasm, Suspicious for High-Grade Urothelial Carcinoma, and High-Grade Urothelial Carcinoma. Each carries a different level of concern. Your oncologist or urologist will use your category alongside your clinical history to decide what happens next.

What does each Paris System category on a urine cytology report mean?

Nondiagnostic (ND): The sample could not be assessed. There were too few cells, or the cells were too degraded to interpret. It gives no information about whether cancer is or is not present. A repeat collection will be needed.
Negative for High-Grade Urothelial Carcinoma (NHGUC): No high-grade cancer cells were seen in this sample. This is the most common result in surveillance programmes. It does not rule out low-grade or early disease entirely, which is why scheduled cystoscopy continues.
Atypical Urothelial Cells (AUC): Some cells look unusual, but not unusual enough to call the result suspicious. This middle-of-the-scale category can be caused by inflammation, infection, kidney stones, or previous treatment — as well as early cancer. Further assessment is needed.
Low-Grade Urothelial Neoplasm (LGUN): The cells suggest a low-grade papillary growth in the bladder lining. High-grade cancer is not indicated, but a cystoscopy is needed to look directly at the bladder and confirm the nature of the finding.
Suspicious for High-Grade Urothelial Carcinoma (SHGUC): The cells look highly abnormal and raise strong concern for high-grade cancer, but a definitive call could not be made from this sample alone. Urgent cystoscopy and further assessment are the typical next steps.
High-Grade Urothelial Carcinoma (HGUC): The cells are consistent with high-grade urothelial cancer. This is the finding the Paris System is designed to detect. Urgent specialist review, cystoscopy, and likely biopsy follow as the immediate next steps.

What does 'Atypical Urothelial Cells' mean on your report?

Atypical Urothelial Cells means the laboratory saw cells that look different from normal, but not different enough to raise high-grade concern. It is not a cancer diagnosis.

Several things cause atypical cells that are not cancer — a urinary tract infection, kidney stones, recent catheterisation, or the effects of prior chemotherapy or radiation on the bladder lining.

Because cancer is one possibility among others, an AUC result almost always prompts further investigation. Your team will usually arrange a cystoscopy or repeat cytology, depending on your history.

Do not read the category in isolation. Your oncologist or urologist will set it against your full clinical picture before deciding the next step.

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What happens after your urine cytology result?

Next steps depend on your category and your clinical history — there is no single pathway that applies to everyone.

A Negative result usually means continuing your scheduled surveillance, which for most people includes periodic cystoscopy at intervals your team has agreed based on your risk.

Atypical or LGUN results commonly lead to a cystoscopy sooner than planned, or a repeat cytology, so the finding can be placed in context.

Suspicious or High-Grade results typically prompt urgent cystoscopy, often within days, and may be followed by biopsy and staging investigations. Your oncology and urology teams will coordinate the next steps.

Questions people most often ask about this result

Why does the Paris System focus on high-grade cancer and not low-grade?

The Paris System was built specifically around detecting high-grade urothelial carcinoma because it is the form that invades the muscle wall of the bladder and becomes life-threatening. Cytology is unreliable for low-grade disease — cells shed from low-grade tumours often look near-normal under the microscope. The system is transparent about this limitation, which is why LGUN is a narrow and infrequently assigned category rather than the main focus.

What do published risk-of-malignancy figures mean?

The Paris System for Reporting Urinary Cytology, 2nd edition (2022), documents risk-of-malignancy ranges drawn from pooled studies across multiple institutions. These figures show what proportion of patients in each category were found to have cancer on follow-up across those populations. They are statistical estimates, not a prediction for any individual. Your doctor reads your category alongside cystoscopy findings, symptoms, and your personal history — the population range is context, not a verdict on your case.

Can a Negative result mean there is definitely no cancer?

Not entirely. A Negative result means no high-grade cancer cells were detected in that sample — not that the bladder is clear. Cytology misses a significant proportion of low-grade papillary tumours because those cells shed infrequently and appear near-normal. This is why cystoscopy remains the primary surveillance tool for most patients with a history of bladder cancer, and a Negative cytology result does not replace it in a monitoring programme.

What should you do if your result was Nondiagnostic?

Nondiagnostic means the sample could not be assessed — typically because too few cells were present, or the cells did not survive collection and processing adequately. It gives no information about whether cancer is or is not there. Your team will arrange a repeat collection, often with specific guidance on how to produce a usable sample. Your surveillance category does not change while you wait, and a Nondiagnostic result does not indicate that anything has worsened.

Is the Paris System used in Indian laboratories?

The Paris System is an international standard, published in 2016 and updated in 2022. Most specialist urology and oncology laboratories in India that issue formal cytology reports use it or terminology aligned with it. If your report uses different words, ask your pathologist or oncologist which Paris System category it corresponds to. That is the category your clinical team will base their decisions on, regardless of the exact language your report uses.

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Common questions

Frequently asked questions

Is a urine cytology report the same as a staging report?

No. Cytology examines individual cells shed into urine to look for abnormal changes. Staging describes how far a tumour has spread — into the muscle wall, to lymph nodes, or beyond. They answer different questions. A cytology report gives no information about stage, and a staging workup involves cystoscopy, imaging, and tissue biopsy — not cytology alone. Your team uses both types of information, but they come from different investigations.

Does an Atypical Urothelial Cells result mean I have bladder cancer?

Not necessarily. The Atypical category includes people who have cancer and people who do not. Inflammation, infection, prior radiation, or chemotherapy can cause cells to look atypical without cancer being present. The result means further investigation is needed to clarify what is causing the change. Your specialist will arrange the appropriate next step — usually cystoscopy or repeat cytology — before drawing any conclusion.

How often is urine cytology done during bladder cancer surveillance?

The frequency depends on your risk category, your tumour history, and what your oncology and urology team have agreed. Frameworks from bodies such as the European Association of Urology describe surveillance schedules based on grade, stage, and recurrence history — but intervals are tailored to each individual. Ask your team how cytology fits into your specific surveillance plan and at what frequency they expect to repeat it.

Can an Atypical or Nondiagnostic result change if the sample is repeated?

Yes. A Nondiagnostic result requires a repeat by definition. An Atypical result can resolve to Negative on a repeat if the cause was temporary — infection or inflammation — or can move to a higher category if the finding reflects a real abnormality. Repeating the test under better conditions, or after treating an underlying infection, gives the laboratory more cells and a clearer picture. Repeat testing is a routine part of managing both these categories.

What does high-grade mean in the context of urothelial cancer?

Grade describes how abnormal cancer cells look compared with normal cells. High-grade cells look very different from normal — they divide rapidly and behave aggressively. High-grade urothelial carcinoma is the form most likely to invade the muscle wall of the bladder and spread to other sites. Low-grade tumours look closer to normal, tend to grow slowly, and rarely invade deeper layers. The Paris System focuses on detecting high-grade disease because it carries the greatest clinical risk.

Should I ask for a second opinion on a borderline cytology result?

For borderline results — particularly Atypical or borderline Suspicious — a second review by another pathologist is a reasonable request. These categories can be genuinely challenging to interpret, and cytology requires specialist training. A second opinion does not significantly delay your care, and it can give your team greater confidence before acting on the result. Ask your oncologist whether review at a specialist centre is appropriate for your case.

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