What this test measures
A 22-25 gauge needle is used to aspirate cells from a lesion (palpable or under ultrasound / CT guidance). Aspirated material is smeared, fixed, stained (Giemsa / Pap / H&E), and examined microscopically. Diagnostic accuracy is high (85-95% sensitivity) for common targets (thyroid, breast lumps, lymph nodes, salivary gland), and the procedure is far less invasive than core biopsy. FNAC distinguishes benign from malignant lesions and can often suggest a specific diagnosis (papillary thyroid cancer, ductal carcinoma, follicular lymphoma, etc.).
Why it matters
FNAC is the first-line diagnostic step for many palpable / radiologically detected nodules in Indian practice — particularly thyroid nodules (Bethesda system standard), breast lumps (Stewart category), enlarged lymph nodes (tuberculous lymphadenitis, lymphoma, metastatic deposits), salivary gland masses, and soft-tissue lumps. Cost-effective alternative to core biopsy for many indications; bedside or radiologist-guided procedure.
How to prepare
Usually outpatient; no fasting required. Disclose any bleeding tendency, anticoagulation (warfarin, DOACs, antiplatelet) — usually FNAC is safe even on anticoagulation given thin needle. The lesion should be palpable or imaging-localized; image-guided FNAC needs separate appointment with radiology.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Cytological Result (Categorical)[1] | Benign / Non-diagnostic / Atypical / Suspicious / Malignant (depending on system) | Benign / Non-diagnostic — re-sample if clinically suspicious; consider core biopsy if uncertain. | Atypical / Suspicious / Malignant — further confirmatory workup (core biopsy, excisional biopsy, surgery). Specific diagnoses (papillary thyroid carcinoma, ductal breast carcinoma, NHL) guide treatment planning. |
Bethesda System for Thyroid Cytopathology
| Category | Risk of malignancy | Action |
|---|---|---|
| I — Non-diagnostic | 5-10% | Repeat FNAC with US guidance |
| II — Benign | 0-3% | Clinical follow-up; US in 12-24 months |
| III — AUS / FLUS | 10-30% | Repeat FNAC or molecular testing |
| IV — Follicular neoplasm | 25-40% | Lobectomy ± molecular testing |
| V — Suspicious for malignancy | 60-75% | Surgery (lobectomy or thyroidectomy) |
| VI — Malignant | 97-99% | Surgery + pre-op staging |
Frequently asked questions
Does FNAC hurt?
Mild discomfort — similar to a venepuncture. Local anaesthetic is rarely needed for superficial lesions. The procedure takes 5-10 minutes.
How accurate is FNAC?
Sensitivity 85-95% for common targets (thyroid, breast, lymph node). False negatives can occur with very small lesions, fibrotic lesions, or sampling error — clinically suspicious lesions warrant repeat FNAC or core biopsy.
What does "non-diagnostic" mean?
Insufficient cells were aspirated for diagnosis — usually requires repeat FNAC, often under image guidance. Common in cystic or fibrotic lesions.
When should I get core biopsy instead?
When FNAC is non-diagnostic, when suspicious follicular thyroid lesion, when lymphoma is the prime concern (cell architecture matters), or for breast lesions where ER/PR/HER-2 immunohistochemistry is needed.
How long for results?
3-5 working days for routine FNAC. Urgent samples can be reported within 24-48 hours.
Will the lump come back?
FNAC doesn't remove or treat the lump — it only samples it. Treatment depends on the cytology diagnosis (surgical excision, medical therapy, or observation).
Related Histopathology / Cytology tests
Tests commonly ordered alongside FNAC, or that help interpret an unexpected result.
Sources & references
- Indian Academy of Cytologists — FNAC Guidelines · accessed 2026-05-30T00:00:00.000Z
- Bethesda System for Thyroid Cytopathology · accessed 2026-05-30T00:00:00.000Z
- College of American Pathologists · accessed 2026-05-30T00:00:00.000Z
- WHO Classification of Tumours · accessed 2026-05-30T00:00:00.000Z
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