Cytology Tests: What They Examine, What They Can and Cannot Tell You

Key takeaways

• Cells, not tissue: Cytology studies loose cells or small cell clusters, so it cannot always show how cells are arranged or whether a tumour has invaded surrounding tissue.
• A normal cytology report is reassuring, not conclusive: Cells may be missed if the sample misses the abnormal area or contains too few cells.
• Several very different procedures share the name "cytology": a Pap smear, a urine sample and a needle aspiration carry different risks and different preparation.
• Abnormal does not mean cancer: many abnormal cytology results reflect infection, inflammation, repair or hormonal change.
• Interpretation belongs with your doctor, who reads the report alongside your symptoms, examination and imaging. Results vary depending on individual clinical circumstances.

At a glance

Also known as

• Cytopathology, cell test, cell study
• FNAC, fine needle aspiration cytology; commonly called "needle test" or "FNAC test" in Indian OPDs
• Pap smear, Pap test, cervical smear, "PAP test"
• Urine cytology, "urine cancer cell test"
• Sputum cytology, "phlegm test", "balgam test"
• Fluid cytology, "pleural fluid test", "ascitic fluid test", "pani ki jaanch" for drained fluid
• LBC, liquid-based cytology

What cytology is

Cytology is a laboratory method in which cells are spread on a glass slide or processed in a liquid medium, stained (commonly with the Papanicolaou or Giemsa stains) and examined under a microscope. The cytopathologist assesses cell size, nuclear features, the nucleus-to-cytoplasm ratio, staining pattern, background material and the presence of organisms or inflammatory cells.

Cytology is deliberately a low-burden test. Samples are usually obtained without a surgical incision, so cytology is often used as a first look when a lump, a fluid collection or an abnormal screening finding needs to be characterised.

Exfoliative cytology

Exfoliative cytology examines cells that shed naturally or are gently scraped or brushed from a surface: cervical smear, urine, sputum, pleural fluid, ascitic fluid, cerebrospinal fluid, bronchial washings, and brushings taken during endoscopy or bronchoscopy.

Aspiration cytology

Aspiration cytology uses a fine needle to draw cells from a palpable or imaged lump, thyroid nodules, breast lumps, enlarged lymph nodes, salivary gland swellings, and lesions in the liver or lung sampled under ultrasound or CT guidance.

Why cytology is done

• Screening: cervical screening by Pap smear or liquid-based cytology, often alongside HPV testing.
• Characterising a lump: FNAC of a thyroid nodule, breast lump, lymph node or salivary gland swelling.
• Investigating fluid: pleural effusion, ascites or cerebrospinal fluid, to look for malignant cells, infection or inflammation.
• Investigating haematuria or bladder symptoms: urine cytology, usually alongside cystoscopy and imaging.
• Identifying infection: tuberculous lymphadenitis, fungal organisms, parasites or viral cytopathic change.
• Follow-up: monitoring for recurrence after treatment of certain cancers, such as surveillance urine cytology in high-grade urothelial carcinoma.

Who should get this test

• Cervical cytology: women and people with a cervix within the screening age range advised by their clinician. Screening intervals and the choice between cytology, HPV testing or co-testing differ between national and hospital programmes, follow the schedule your doctor gives you.
• FNAC: anyone with a new, enlarging or persistent lump in the neck, thyroid, breast, salivary gland or lymph nodes, or a nodule found on imaging that meets criteria for sampling.
• Urine cytology: people with visible or persistent microscopic blood in urine, unexplained irritative urinary symptoms, occupational exposure to aromatic amines or dyes, or follow-up after bladder cancer.
• Sputum cytology: selected people with a persistent cough, blood-stained sputum or an abnormal chest image who cannot easily undergo bronchoscopy or biopsy.
• Fluid cytology: anyone having a pleural or peritoneal fluid drained for diagnosis.
• Not suitable as a general "cancer check": cytology is not a whole-body screening test and should not be ordered without a specific clinical question.

What cytology cannot detect or exclude

• Cytology cannot reliably show invasion. Distinguishing carcinoma in situ from invasive cancer usually requires a tissue biopsy (histopathology), because tissue architecture must be seen intact.
• A negative cytology result does not exclude cancer. The needle or brush may have missed the abnormal area, or too few diagnostic cells may have been obtained. "No malignant cells identified" means none were seen in the material examined, not that none exist.
• Urine cytology is relatively insensitive for low-grade urothelial tumours. A normal urine cytology does not exclude bladder cancer; cystoscopy and imaging remain central.
• Sputum cytology has limited sensitivity for peripheral lung lesions. A normal result does not exclude lung cancer; CT, bronchoscopy or image-guided biopsy may still be needed.
• A single negative fluid cytology does not exclude malignant effusion. Sensitivity improves with larger volumes and repeat sampling, but remains incomplete.
• Thyroid FNAC cannot separate follicular adenoma from follicular carcinoma. That distinction depends on capsular and vascular invasion seen only on surgical histology.
• Cytology does not provide all the information needed to plan cancer treatment. Tumour grade, stage, margins and many biomarker studies often need a core biopsy or resection specimen, though some ancillary tests can be run on cell blocks.
• Cytology does not diagnose tuberculosis definitively on its own. Granulomas on cytology are suggestive; confirmation usually needs AFB staining, culture or a molecular test such as Xpert MTB/RIF.
• Inadequate or non-diagnostic samples happen. A repeat procedure is common and does not mean something was done wrongly.

If your symptoms persist despite a normal cytology report, go back to your doctor. Normal cells on a slide do not overrule a worrying clinical picture.

Related but different examinations

FNAC versus core needle biopsy: these are different procedures, not a lesser and greater version of the same one. FNAC uses a very thin needle and gives cells; core biopsy uses a wider cutting needle and gives a small tissue cylinder. For breast lumps and many soft-tissue lesions, core biopsy is often preferred because it can show invasion and allow receptor testing. For thyroid nodules and reactive lymph nodes, FNAC is frequently the appropriate first step. The right choice depends on the clinical problem.

How to prepare

Preparation is set by the unit performing the test and by the site being sampled. The instructions you are given at your appointment take precedence over any general guidance.

Cervical cytology (Pap smear / LBC)

• Units commonly advise avoiding intercourse, vaginal medicines, douching and vaginal lubricants for about 24-48 hours beforehand.
• Heavy menstrual bleeding can obscure the sample; many units prefer to reschedule, though a smear can still be taken if there is a clinical reason.
• Tell the clinician about pregnancy, recent cervical treatment, hysterectomy or pelvic radiotherapy.

Fine needle aspiration cytology

• Superficial FNAC of thyroid, breast or neck nodes usually needs no fasting and no special preparation.
• Deep FNAC under ultrasound or CT guidance, or FNAC requiring sedation, may involve fasting instructions from the unit.
• Tell the team about blood thinners such as warfarin, clopidogrel, aspirin or a DOAC, about bleeding disorders, and about any allergy to local anaesthetic. Do not stop any prescribed medicine on your own, only the prescribing doctor should change it.

Urine cytology

• A clean-catch, mid-stream sample is usual. Early-morning first-voided urine is often discouraged for cytology because overnight cells degenerate; many units prefer a second-morning specimen.
• Some units ask for samples on separate days.
• Caution on "drink plenty of water": people with heart failure, advanced chronic kidney disease, dialysis-related fluid restriction or a doctor-advised fluid limit should not increase fluid intake for a test. Ask the unit how to proceed.

Sputum cytology

• Rinse the mouth with plain water first so the sample is not diluted by saliva and food debris.
• A deep cough from the chest is needed; saliva is not an adequate sample.
• Induced sputum using nebulised saline may be arranged if you cannot produce a sample. Tell staff if you have asthma or COPD, as induction can provoke wheeze.

Special-population caveats

• Diabetes on glucose-lowering therapy: if a procedure requires fasting, ask the prescriber in advance how to handle insulin or tablets on the day. Do not fast for long periods without that advice.
• Children: paediatric FNAC may need a parent present, topical anaesthetic or sedation; preparation differs from adult protocols.
• Pregnancy: cervical cytology and most superficial FNACs can be performed in pregnancy when indicated. Inform the team; CT-guided procedures are usually deferred or replaced with ultrasound guidance.
• Anticoagulated or frail older adults: the team may plan extra compression time and a longer observation period.

What happens during the test

Cervical smear: you lie on a couch, a speculum is inserted and a brush or spatula collects cells from the cervix. Sampling takes under a minute; the whole appointment is usually 5-10 minutes. Mild cramping or light spotting afterwards is common.

FNAC: the skin is cleaned, local anaesthetic may be used, and a thin needle is passed into the lump. Two to four passes are often needed to get enough cells. Expect pressure and brief sharp discomfort. Most superficial FNACs take 10-20 minutes including preparation and pressure afterwards; ultrasound- or CT-guided procedures take longer and include an observation period.

Fluid cytology: fluid is collected during a pleural tap, ascitic tap or lumbar puncture. The cytology part adds no extra procedure; timing depends on the drainage itself.

Urine and sputum: you collect the sample yourself into a sterile container, usually within a few minutes.

In the laboratory: slides are prepared, fixed, stained and screened by a cytotechnologist and a pathologist. Additional stains, cell blocks, immunocytochemistry or molecular tests may be added, which extends reporting time. Ask your unit when your report is expected.

Understanding your cytology report

Cytology reports are descriptive. They usually state whether the sample was adequate, describe what was seen, and give a diagnostic category with a recommendation.

• Satisfactory / unsatisfactory for evaluation: an unsatisfactory or non-diagnostic sample means too few or poorly preserved cells. A repeat is usually advised.
• Negative for malignancy: no cancer cells were seen in the material examined. This is not the same as cancer having been excluded.
• Inflammatory / reactive changes: cells altered by infection, healing, hormonal change or an intrauterine device. Usually benign.
• Atypical cells / atypia of undetermined significance: the cells are not clearly normal and not clearly malignant. This is a common, deliberately cautious category and often leads to repeat sampling, HPV testing or biopsy rather than to a cancer diagnosis.
• Suspicious for malignancy: features point towards cancer but fall short of certainty. Confirmation by biopsy is usual.
• Positive / malignant cells identified: cancer cells were seen. Further tests define the type, origin and extent.

Structured reporting systems are used at specific sites, the Bethesda System for cervical cytology and for thyroid cytology, the Paris System for urinary cytology, and the IAC Yokohama System for breast cytology. Each assigns a category with an implied management pathway. If your report quotes a category number, ask your doctor what that category means in your situation. Never treat a category number as a diagnosis on its own.

When cytology results can be misleading

Falsely reassuring (false negative)

• Sampling error: the needle or brush missed the abnormal focus, the single commonest cause.
• Scanty or degenerate cells: delayed transport, poor fixation or air-drying artefact.
• Low-grade tumours shed bland-looking cells: particularly low-grade urothelial carcinoma, which urine cytology often cannot flag.
• Cystic lesions: aspirating only fluid from a cystic thyroid or breast lesion can miss a solid tumour in the wall.
• Heavy blood, pus or necrosis obscuring the diagnostic cells.
• Peripheral lung lesions that do not communicate with the airways shed few cells into sputum.

Falsely alarming (false positive or over-called atypia)

• Infection and inflammation: including trichomonas, candida, bacterial vaginosis and herpes, can make cervical cells look atypical.
• Recent radiotherapy or chemotherapy produces marked reactive cell changes that mimic malignancy.
• Urinary stones, catheters, recent instrumentation and intravesical BCG commonly cause reactive urothelial atypia.
• Repair and regeneration after surgery or injury produces enlarged, active-looking nuclei.
• Atrophic changes after menopause can mimic abnormal cervical cells.
• Pregnancy-related changes in cervical cytology can be misread without clinical information.

Give the laboratory your clinical history, medicines, and any recent procedure or treatment. Cytology read without context is far more likely to mislead.

Risks and safety

Risk depends entirely on how the sample is obtained. These are different procedures with different risk profiles.

Non-invasive samples (urine, sputum)

No physical risk beyond discomfort from coughing. Sputum induction may provoke wheeze in people with asthma or COPD.

Cervical smear

Mild cramping, spotting for a day or two, and brief discomfort are common. Infection is uncommon. Bleeding may be more noticeable in pregnancy or with cervical inflammation.

Fine needle aspiration

Bruising, soreness and small haematomas are the usual events. Infection is uncommon. Site-specific risks include pneumothorax with lung or deep neck aspirates, bleeding after liver aspiration, and transient swelling after thyroid FNAC. Risk is higher with bleeding disorders or anticoagulation. Needle-track seeding is very rare with fine needles but is one reason certain lesions are not aspirated.

Fluid sampling procedures

Pleural, peritoneal and lumbar puncture procedures carry their own risks, pneumothorax, bleeding, infection or post-procedure headache, discussed as part of consent for that procedure rather than for the cytology itself.

Diagnostic risk

False negatives, false positives, atypical results and non-diagnostic samples all occur with cytology. Results vary depending on individual clinical circumstances, sample quality and the site examined.

Special situations

Pregnancy

Cervical cytology can be performed in pregnancy when indicated; endocervical brushes are often used cautiously. Superficial FNAC of thyroid, breast or neck lumps is generally acceptable with ultrasound guidance. CT-guided sampling is avoided unless there is no alternative. Pregnancy alters breast and cervical cytology appearances, always tell the laboratory you are pregnant.

Children

FNAC of neck nodes is common in children, frequently for reactive nodes or tuberculous lymphadenitis. Sedation or topical anaesthetic is used more often. Paediatric lesions have a different differential diagnosis, so paediatric-experienced reporting matters.

Older adults

Atrophic changes affect cervical cytology and can generate atypical reports. Anticoagulant use is more common, so bleeding risk after aspiration is higher. Frailty may influence whether an abnormal result is pursued with further invasive testing.

People on anticoagulants or antiplatelets

Tell the team before the appointment. Fine needle aspiration of superficial sites is often possible without stopping medication, but the decision rests with your treating doctor. Do not stop the medicine yourself.

Chronic kidney disease, heart failure and fluid restriction

Do not follow generic "drink lots of water" advice before urine cytology. Ask the unit how to produce an adequate sample within your fluid limit.

Immunocompromised patients

Infections such as tuberculosis, cryptococcus, pneumocystis and CMV are more likely and may be found on cytology. Cancer risk is also higher, so atypical results are usually pursued more actively.

Cytology in the Indian context

• Tuberculosis dominates lymph node cytology. FNAC of an enlarged cervical lymph node is one of the most frequently performed cytology procedures in India. Granulomatous inflammation with necrosis raises suspicion of tuberculosis, but cytology alone is not confirmatory, AFB staining, culture or Xpert MTB/RIF on the aspirate is generally added.
• Cervical cancer remains a major cause of cancer deaths in Indian women. National programme guidance under the NP-NCD framework supports population-level cervical screening; the method offered (visual inspection with acetic acid, cytology or HPV testing) varies between states and facilities. Follow the pathway your treating centre uses.
• Terminology you will hear: "FNAC test", "PAP test", "biopsy" used loosely for FNAC, and "phlegm test" for sputum cytology. FNAC and biopsy are not the same procedure, clarify which one has been advised.
• Thyroid nodules are common, partly linked to iodine status in some regions, and thyroid FNAC is a high-volume test. Most such nodules are benign.
• Tobacco use, including smokeless forms such as gutkha and khaini, drives a large burden of oral and head-and-neck lesions where cytology and brush sampling may be used as an initial step, with biopsy remaining the confirmatory test.
• PC-PNDT Act 1994: where cytology sampling is performed under ultrasound guidance, the ultrasound facility and operator must comply with PC-PNDT registration and record-keeping requirements. Determination of foetal sex is a criminal offence in India.

Cost and insurance in India

Costs differ widely between government facilities, trust hospitals, standalone laboratories and large private hospitals. Charges are usually quoted per test, and additional charges apply for imaging guidance and ancillary studies. Ask for a written estimate before the procedure.

What drives the cost

• Type of sample: a self-collected urine or sputum sample costs far less than an image-guided aspiration.
• Imaging guidance: ultrasound guidance adds cost; CT or endoscopic ultrasound guidance adds considerably more.
• Preparation method: liquid-based cytology usually costs more than a conventional smear.
• Add-on tests: cell block preparation, immunocytochemistry, special stains, HPV testing, flow cytometry and molecular studies are billed separately and can exceed the cost of the base cytology.
• Setting: government and subsidised screening programmes may offer cervical screening free or at nominal cost. Day-care or sedation requirements add facility charges.
• Repeat sampling: a non-diagnostic sample may require a repeat, with repeat charges.

Insurance

Outpatient diagnostic tests are frequently not covered by standard indemnity health insurance unless linked to an admission or covered by an OPD rider. When cytology is performed as part of an admitted procedure, it is usually part of the hospitalisation claim. Government schemes such as Ayushman Bharat PM-JAY cover defined packages at empanelled hospitals. Confirm coverage with your insurer or the hospital's TPA desk before proceeding.

Myths and facts

Frequently asked questions

What is cytology used for?

Cytology examines cells to answer a defined clinical question: is this lump benign or malignant, is this fluid infected or malignant, are there abnormal cervical cells. Cytology supports screening, diagnosis and follow-up, but a tissue biopsy is usually needed to confirm cancer type and invasion before treatment begins.

How long does a cytology procedure take?

Collecting a urine or sputum sample takes a few minutes. A cervical smear appointment usually runs 5-10 minutes, with under a minute of actual sampling. A superficial fine needle aspiration typically takes 10-20 minutes including preparation and pressure afterwards. Ultrasound- or CT-guided aspirations take longer and include an observation period.

Is cytology painful?

Most cytology sampling causes brief discomfort rather than pain. A cervical smear may cause cramping and pressure. Fine needle aspiration produces a short sharp sensation and soreness for a day or two. Local anaesthetic is used for some deeper aspirations. Pain tolerance and experience vary between individuals.

What does an "atypical" cytology result mean?

Atypical means the cells are neither clearly normal nor clearly cancerous. It is a deliberately cautious category used when features are ambiguous or the sample is limited. It usually leads to repeat sampling, additional testing such as HPV testing, or a biopsy. Atypical is not a cancer diagnosis.

What is the difference between cytology and histopathology?

Cytology examines loose cells; histopathology examines intact tissue. Because histopathology preserves architecture, it can show whether a tumour has invaded surrounding tissue and allows grading and margin assessment. Cytology is quicker and less invasive, so it is often the first step, with histopathology used for confirmation.

Can cytology detect every cancer?

No. Cytology depends on abnormal cells reaching the sample. Deep-seated tumours, small peripheral lung lesions, low-grade bladder tumours and follicular thyroid lesions are frequently missed or cannot be classified by cytology alone. Imaging, endoscopy and tissue biopsy fill these gaps depending on the clinical problem.

My cytology sample was "inadequate". Did something go wrong?

Not usually. Inadequate or non-diagnostic samples happen when too few cells are obtained, when a lesion is cystic or fibrous, or when blood obscures the slide. A repeat procedure is standard, sometimes with ultrasound guidance to improve targeting. It does not mean the result was bad news.

Do I need to stop my blood thinner before FNAC?

Do not stop any prescribed medicine on your own. Many superficial fine needle aspirations are performed without stopping anticoagulants or antiplatelets. The decision depends on the site, the needle size and why the medicine was prescribed. Inform the team well in advance so the prescribing doctor can advise.

Can cytology be done during pregnancy?

Cervical cytology and ultrasound-guided superficial fine needle aspiration can generally be performed during pregnancy when clinically indicated. CT-guided sampling is usually avoided. Pregnancy changes the appearance of cervical and breast cells, so tell both the clinician and the laboratory that you are pregnant.

Sources

• Nayar R, Wilbur DC (eds). The Bethesda System for Reporting Cervical Cytology, definitions, criteria and explanatory notes.
• Ali SZ, Cibas ES (eds). The Bethesda System for Reporting Thyroid Cytopathology.
• Barkan GA, Wojcik EM, Rosenthal DL et al. The Paris System for Reporting Urinary Cytology.
• International Academy of Cytology, Yokohama System for Reporting Breast Fine Needle Aspiration Biopsy Cytopathology.
• World Health Organization. Guideline for screening and treatment of cervical pre-cancer lesions for cervical cancer prevention.
• Ministry of Health and Family Welfare, Government of India, Operational Framework: Management of Common Cancers (cervical, breast, oral).
• Pre-conception and Pre-natal Diagnostic Techniques (Prohibition of Sex Selection) Act, 1994, Government of India.
• Indian Council of Medical Research, National Cancer Registry Programme reports.<