Understanding your report

Cytology Reporting Systems — Explained

Your cytology report gives a category — a number or letter — instead of a plain yes or no. That is not evasion; it is an honest statement of how much certainty a cell sample can carry. Each category maps to a published risk range, and the system used depends on where your sample was taken.

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Not a final diagnosis — A cytology category describes a level of suspicion. For most categories, a biopsy or further investigation is the next step, not an immediate conclusion.
The system depends on the body site — Thyroid, cervical, urine, and salivary gland samples each use a different named reporting system with different category labels.
Each category has a published risk range — These ranges come from large studies and are stated in international guidelines. They describe populations, not your individual result.
Your specialist interprets your result — The category is the starting point. Your imaging, symptoms, and medical history complete the picture.

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Cytology results are given as categories — not a plain yes or no — because reading individual cells carries more uncertainty than a tissue biopsy. Each category maps to a published malignancy risk range. Which system applies depends on where your sample was taken: thyroid, cervix, urine, and salivary gland each use a different named system.

Why does a cytology result come as a category instead of a plain answer?

Cytology examines cells collected through a fine needle, a swab, or a fluid sample — a smaller picture than a surgical biopsy. Because the sample is limited, the level of certainty varies, and the category system captures that honestly.

Each category sits on a scale from clearly normal to clearly suspicious, with intermediate categories for results that fall between the two. The category guides what your team does next.

For intermediate and high-suspicion categories, a biopsy or surgery is what produces the definitive answer. Cytology is a step toward that, not the final word.

Which reporting system applies to which body site?

Thyroid FNAC: The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC), third edition 2023. Uses six categories numbered I to VI, from non-diagnostic to malignant.
Cervical smear (Pap test): The 2014 Bethesda System for Reporting Cervical Cytology. Uses letter codes — NILM, ASC-US, ASC-H, LSIL, HSIL, AGC — rather than numbers.
Urine cytology: The Paris System for Reporting Urinary Cytology (TPS), second edition 2022. Designed specifically to detect high-grade urothelial carcinoma; uses descriptive category names.
Salivary gland FNAC: The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC), second edition 2023. Categories I to VI, with category IV split into IVA and IVB.
Sputum and body fluids: May use the International System for Reporting Serous Fluid Cytopathology (TIS, 2020) or descriptive reporting. Check the report header or ask your pathologist which was applied.

What does the category number or letter actually mean?

Each system assigns a label — a Roman numeral, a letter code, or a descriptive name — on a scale of suspicion. Lower or benign labels reflect normal or near-normal findings. Higher or suspicious labels reflect a greater degree of concern.

Every category comes with a published malignancy risk range, calculated from large studies of patients who went on to surgery. That range describes what proportion of people in that category turned out to have cancer — it is not a prediction for you individually.

Your oncologist weighs the category alongside your imaging and clinical history before recommending any next step. The category opens the conversation; it does not close it.

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What should you do when you receive a cytology report?

Note the exact category name and number as written on the report.
Check which reporting system your laboratory used — usually named in the report header.
Do not compare your category to someone else's result from a different body site or a different system.
Bring the original printed report to your specialist appointment, not a photograph or a verbal summary.
Ask your oncologist what the published malignancy risk range is for your specific category.
Ask what the recommended next step is for your category and your clinical situation.

What are the categories in each main reporting system?

Thyroid FNAC: Bethesda System categories (TBSRTC, 2023)

Category I — Non-diagnostic: insufficient cells; repeat aspiration recommended. Category II — Benign: cells appear normal; monitoring continues. Category III — Atypia of Undetermined Significance (AUS): cells are unusual without meeting benign or suspicious criteria; repeat aspiration or molecular testing may follow. Category IV — Follicular Neoplasm: a growth pattern that cannot be classified as benign without examining full tissue; surgery often advised. Category V — Suspicious for Malignancy: strong suspicion without full diagnostic criteria; surgery usually recommended. Category VI — Malignant: cancer cells identified; specific type guides surgical planning. Malignancy risk ranges for each category are published in the TBSRTC 2023 guidelines.

Cervical smear: Bethesda System categories (2014)

NILM: no abnormal cells; routine screening continues. ASC-US: minor changes usually related to HPV; reflex HPV testing follows. ASC-H: atypical cells that cannot exclude high-grade change; colposcopy recommended. LSIL: changes consistent with HPV infection; managed by surveillance or colposcopy depending on age and history. HSIL: more significant changes; colposcopy and biopsy are the usual next step. AGC: glandular cell changes needing further evaluation, including endometrial sampling in some cases. AIS or Malignant: specialist referral follows. Management pathways are set out in ASCCP guidelines, updated 2019.

Urine cytology: Paris System categories (TPS, 2022)

Non-diagnostic: insufficient cells; repeat sample needed. NHGUC (Negative for High-Grade Urothelial Carcinoma): no high-grade cancer cells found. AUC (Atypical Urothelial Cells): abnormal cells not sufficient to diagnose high-grade disease; cystoscopy may be recommended. SHGUC (Suspicious for High-Grade Urothelial Carcinoma): features strongly suggest high-grade cancer; further evaluation recommended. HGUC (High-Grade Urothelial Carcinoma): cells meet diagnostic criteria for high-grade cancer. LGUN (Low-Grade Urothelial Neoplasm): a separate category for low-grade growths. The Paris System is designed specifically to detect high-grade disease, treating high-grade and low-grade findings as distinct pathways.

Salivary gland FNAC: Milan System categories (MSRSGC, 2023)

Category I — Non-diagnostic: insufficient material; repeat aspiration recommended. Category II — Non-neoplastic: benign or inflammatory changes. Category III — Atypia of Undetermined Significance: unusual features without a clear pattern; repeat or surveillance may follow. Category IVA — Benign Neoplasm: appears benign on cell examination; surgery may still be needed depending on size and type. Category IVB — Salivary Gland Neoplasm of Uncertain Malignant Potential (SUMP): behaviour cannot be predicted from cells alone; surgery typically advised. Category V — Suspicious for Malignancy: surgical excision usually planned. Category VI — Malignant: specific cancer type guides management.

Did you know?

The word 'atypia' appears in the thyroid Bethesda, cervical Bethesda, Milan, and Paris systems — but it describes different cell types and carries a different published malignancy risk range in each one.

The category number alone does not tell you the risk without knowing which reporting system produced it.

Source: International Academy of Cytology consensus documents and individual system design publications

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Common questions

Frequently asked questions

What does Category III mean on a thyroid cytology report?

Category III in the thyroid Bethesda system is called Atypia of Undetermined Significance (AUS). It means cells look unusual without fitting the benign or suspicious categories clearly — an honest in-between result. TBSRTC 2023 guidelines describe a malignancy risk range for this category that is wider than for the clearer categories, because the result is less certain. Most patients at this stage are advised to have a repeat aspiration, molecular testing, or both before any surgical decision is made.

Does a cervical smear result mean I have cancer?

Very rarely, and the category tells you. NILM — the most common result — means no abnormal cells were seen. Higher categories such as LSIL and HSIL describe changes that need further investigation, but they are not cancer diagnoses. Even HSIL requires colposcopy and biopsy to confirm what is happening. Cervical cytology is a screening test. The Bethesda categories guide the next investigation step; they do not deliver a final diagnosis.

What does 'atypia of undetermined significance' mean?

Atypia means cells look unusual — between normal and clearly abnormal — without fitting benign or suspicious criteria. The phrase appears in multiple systems: Category III in the thyroid and Milan systems, ASC-US for squamous cells, and AGC for glandular cells in the cervical Bethesda. In every system it is an honest acknowledgement of uncertainty, not a finding you can interpret in either direction. The recommended next step depends on your specific site and system — ask your oncologist directly.

Can I get a second opinion on a cytology result?

Yes, and it is reasonable to ask for one. Intermediate categories — where cells are unusual but not clearly abnormal — can be read differently by different pathologists. Sending your slides and report to a second laboratory for review is standard practice, not a sign of distrust. A second opinion is most useful for Category III or IV thyroid results, ASC-H or AGC cervical results, and any result where surgery is being recommended on the basis of the cytology alone.

What is the difference between a cytology report and a biopsy report?

Cytology examines individual cells from a fine needle, swab, or fluid sample. A biopsy removes a piece of tissue and examines how cells are arranged together — the architecture. Architecture provides more information, so a biopsy can usually give a more definitive answer. Most cytology category systems are designed to guide whether a biopsy or surgery is needed. A cytology report is a step toward a diagnosis, not always the final one.

Does a high category number always mean I need surgery straight away?

Not automatically. The category is one factor. Your oncologist weighs it alongside imaging, symptoms, general health, and sometimes molecular testing from the sample itself. Some high-suspicion categories are managed with a repeat aspiration or surveillance before surgery is planned. Some intermediate categories lead to surgery because of what the imaging shows, not the category alone. Ask specifically what your category means in the context of your full clinical picture.

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