A minimally invasive, low-complication diagnostic method in which cell samples are obtained with a fine needle from superficial masses or those accessible under imaging guidance, then evaluated cytologically.
Indication
- Evaluation of thyroid nodules according to the Bethesda classification
- Preliminary diagnosis to differentiate benign from malignant breast masses
- Investigation of enlarged lymph nodes (lymphadenopathy) in the neck region
- Pre-subtyping evaluation of salivary gland masses
- Diagnosis of superficial soft tissue masses and cysts
- Cell sampling from deep lesions of the lung and liver under CT or ultrasound guidance
Preparation
- Use of blood-thinning medications is reviewed; if necessary, temporarily discontinued with physician approval
- Localization of the lesion by ultrasound or physical examination
- Informing the patient about the procedure and obtaining consent
- Routine blood tests (especially coagulation) are requested before the procedure if needed
How it's performed
- The procedure area is cleaned and local anesthesia is applied if needed (often not required)
- The mass is stabilized by ultrasound guidance or palpation
- A fine needle (typically 22-27 G) is advanced into the lesion, and cells are aspirated under gentle negative pressure
- Generally 2-4 separate passes are performed; each sample is spread onto a slide
- Samples are fixed in air or with alcohol; rapid staining may be used to assess sample adequacy
- The cytopathologist issues a report using standard classifications such as Bethesda (for thyroid)
Post-procedure
- Compression is applied for 5-10 minutes after the procedure
- Mild bruising or tenderness at the needle entry site usually resolves within 1-2 days
- For thyroid FNAB, follow-up or surgery is planned according to the Bethesda category
- In cases of insufficient sample (Bethesda I), a repeat procedure under ultrasound guidance is recommended after 3 months
- For suspicious or malignant results, further evaluation or surgical referral is arranged
Risks
- Mild pain, bruising, or small hematoma (common, resolves spontaneously)
- Possibility of repeating the procedure due to insufficient cell sampling
- Superficial skin infection (very rare, minimized with aseptic technique)
- Vasovagal reaction (sensation of fainting) — temporary
- Injury to neighboring structures in deep lesions (rare in image-guided cases)
FAQ
Is FNAB painful?
The needle is not thick; for most patients it causes discomfort similar to a blood draw. Local anesthesia is rarely required.
How long does it take to get the FNAB result?
Cytologic evaluation is generally completed within 3-7 business days. In some centers, rapid adequacy assessment is performed during the procedure.
What do the Bethesda categories mean?
The Bethesda system evaluates thyroid FNAB results in six categories (non-diagnostic, benign, atypia, follicular neoplasm, suspicious, malignant). Each category requires a different follow-up or treatment approach.
Is surgical biopsy needed instead of FNAB?
When FNAB is sufficient for preliminary diagnosis, unnecessary surgery is avoided. However, in suspicious, inadequate, or cases requiring definitive diagnosis, core (large needle) biopsy or surgical excision may be recommended.
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