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Understanding your pathology report

Cytology and Prostate Scoring Systems — What Each Category Means

When a biopsy or cytology report uses terms like Bethesda Category IV or ISUP Grade Group 3, it is using a named scoring system to place your result on a risk scale. This page explains what each of the five main systems is, what its categories mean, and what typically happens next.

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

  • Five systems, five tissue types — Bethesda covers thyroid; Paris covers urinary tract; Milan covers salivary glands; Sydney covers gastric tissue; Gleason and ISUP Grade Groups cover prostate.
  • Risk bands, not diagnoses — Each category describes where a result sits on a risk scale. It is a starting point for your team's decision-making, not a diagnosis on its own.
  • Next steps are built in — Every category in every system links to a recommended management path — from monitoring to repeat biopsy to surgical referral.
  • Population figures, not your figure — Published malignancy risk ranges describe how often a category turned out to be cancer across large groups of patients — not your individual probability.
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Bethesda, Paris, Milan, Sydney and Gleason are standardized systems that pathologists use to group cytology and biopsy findings into named risk categories. Each category carries a published malignancy risk range and a recommended next step — monitoring, repeat sampling, or surgical referral. They exist to standardize language so a result means the same thing across hospitals.

Why do pathologists use these named scoring systems?

Before standardized systems existed, the word 'suspicious' on a pathology report meant something different at each hospital. One pathologist's intermediate category was another's high-risk one.

Named systems give every category a precise published definition. A Bethesda Category III thyroid result from a lab in Hyderabad carries the same clinical meaning as one from a lab anywhere else in the world.

Each system also links its categories to a published malignancy risk range and a management recommendation, drawn from large multi-centre studies. That is why your oncologist can describe what usually happens next at a given category, before your own follow-up results are in.

Each system covers a specific tissue site. Bethesda was developed for thyroid fine-needle aspirates. Paris was developed for urine cytology. Milan covers salivary gland aspirates. The Updated Sydney System classifies gastric biopsies taken at endoscopy. The Gleason score and ISUP Grade Groups are used for prostate biopsies only.

What does each scoring system's risk scale look like?

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC), revised in 2017, has six categories. Category I means the sample did not contain enough cells for a reliable result. A repeat fine-needle aspirate is usually recommended. Category II is benign and carries the lowest published malignancy risk. Categories III and IV sit in an intermediate zone — atypia of undetermined significance and follicular neoplasm — where the risk is higher than benign and further workup is needed. Category V is suspicious for malignancy. Category VI is reported as malignant. Categories V and VI typically lead to surgical referral.

The Paris System for Reporting Urinary Cytology, published by the International Society of Urological Pathology, focuses on detecting high-grade urothelial carcinoma in urine samples. A result reported as negative for high-grade urothelial carcinoma (NHGUC) carries a low risk. Atypical urothelial cells (AUC), suspicious (SHGUC) and positive (HGUC) results carry progressively higher risk. Suspicious and positive results typically prompt cystoscopy if it has not already been performed. The system was designed to reduce over-reporting of low-grade lesions that rarely progress to invasive cancer.

The Milan System for Reporting Salivary Gland Cytopathology, published in 2018, uses six categories from non-diagnostic to malignant. Categories I and II carry low risk. The intermediate categories — atypia of undetermined significance (AUS) and salivary gland neoplasm of uncertain malignant potential (SUMP) — usually lead to repeat aspiration or surgical excision for a definitive answer. Categories V and VI carry high malignancy risk and prompt surgical review.

The Updated Sydney System classifies gastric biopsies taken at endoscopy. It grades inflammation, H. pylori density, glandular atrophy, intestinal metaplasia, and dysplasia. Dysplasia is the feature most directly linked to cancer risk. Low-grade dysplasia is typically monitored with repeat endoscopy at intervals your team will specify. High-grade dysplasia is considered pre-malignant and is usually treated by endoscopic or surgical removal.

ISUP Grade Groups for prostate were endorsed by the International Society of Urological Pathology in 2014 and implemented globally from 2016. They replaced the older Gleason sum score, which was confusing because nearly all results fell in the upper half of its range. Grade Group 1 represents the lowest-risk prostate disease and is often managed with active surveillance. Grade Groups 2 and 3 sit in an intermediate range where the choice between surveillance and active treatment is individualized. Grade Groups 4 and 5 represent high-risk disease and usually prompt a discussion about active treatment.

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What questions should I ask after getting my cytology or pathology report?

  • Ask which scoring system was used and which category or grade group your result falls into.
  • Ask whether the sample was adequate — a non-diagnostic result means the sample needs repeating, not that cancer has been found.
  • Ask what the recommended next step is for your category, and how soon it needs to happen.
  • Ask which guideline body sets the malignancy risk range for your category.
  • Ask how to arrange a second opinion on the pathology reading if you want one.
  • Write down the system name, category number and grade before you leave — you will need it at every future consultation.

Did you know?

The Bethesda System for Reporting Thyroid Cytopathology was established after a 2007 National Cancer Institute conference, replacing a fragmented landscape of locally defined terms.

Before it existed, the same thyroid slide could be described as 'insufficient', 'inadequate', or 'unsatisfactory' depending on the hospital — making it impossible to apply consistent management guidance or to compare results between centres.

Source: The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC), National Cancer Institute 2007, revised 2017

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Common questions

Frequently asked questions

What is the Bethesda system and what do its six categories mean?

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) groups thyroid fine-needle aspirate results into six categories. Category I (non-diagnostic) means the sample did not contain enough cells for assessment and a repeat is needed. Category II (benign) carries the lowest published malignancy risk. Categories III and IV sit in an intermediate zone where further workup is needed before any decision. Category V (suspicious) and Category VI (malignant) carry substantially higher risk and typically lead to surgical referral. The 2017 TBSRTC revision updated the malignancy risk ranges for each category. Your own result needs to be interpreted by your treating clinician alongside your imaging and clinical history — a category number alone is not a diagnosis.

What is the difference between a Gleason score and an ISUP Grade Group?

The original Gleason score added the grades of the two most common cell patterns in a prostate biopsy to give a sum. In practice, nearly all results fell in the upper half of the scale, which made lower numbers misleading — a Gleason 6 sounds middling but represents the lowest-risk disease. The ISUP Grade Group system, endorsed by the International Society of Urological Pathology in 2014 and used clinically from 2016, replaced the sum with five groups numbered 1 (lowest risk) to 5 (highest). Most modern prostate biopsy reports carry both. If yours shows only one, ask your team what the corresponding grade group is.

What does atypical mean on a cytology report?

Atypical means the cells examined look different from normal but are not clearly cancerous. It is an intermediate category that appears in most of these systems under different names — atypia of undetermined significance (AUS) in Bethesda and Milan, atypical urothelial cells (AUC) in Paris. It is not a diagnosis of cancer, and it is not a clean result either. The next step depends on which system was used and which tissue site was sampled, but typically involves repeat sampling, additional imaging, or a more definitive surgical biopsy. Ask your team specifically what the recommended next step is for your category and site.

What happens after a non-diagnostic cytology result?

A non-diagnostic result — Category I in both Bethesda and Milan — means the laboratory could not make a reliable assessment from the sample collected. This usually happens because the sample did not contain enough cells, or because blood or other material obscured them. It does not mean cancer has been found. The usual next step is a repeat fine-needle aspirate, often with ultrasound guidance to improve sample quality. If repeat samples remain non-diagnostic, your team may recommend a surgical excision to obtain tissue large enough for full histopathological assessment.

Can a Category II Bethesda result still turn out to be cancer?

Category II is the benign category and carries the lowest published malignancy risk of any interpretable Bethesda result, as set out in the 2017 TBSRTC revision. However, cytology is a sampling procedure — not every cell in a nodule is examined — so no cytology category carries a risk of exactly zero. This is why even a benign Bethesda result usually requires follow-up imaging after a period of time rather than complete discharge. Your team will specify how frequently your nodule should be monitored, based on its size, ultrasound features, and your overall clinical picture.

Does a high ISUP Grade Group mean the cancer has spread?

No. The ISUP Grade Group describes the aggressiveness of the cells seen under the microscope — how abnormal they look — not whether the disease has spread beyond the prostate. Grade and stage are two separate pieces of information. A high-grade cancer (Grade Group 4 or 5) that remains entirely within the prostate is still localized disease. A lower-grade cancer can in some circumstances have already spread. Your oncologist will interpret grade and stage together, alongside PSA levels and imaging findings, before recommending how to proceed.

Full index

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