Fine Needle Aspiration Biopsy (FNAB) is a diagnostic procedure guided by imaging or performed blindly, primarily involving the extraction of tissue or fluid samples through a fine needle for cytological analysis. This technique is minimally invasive and commonly used to evaluate neoplastic lesions, infections, or inflammatory sites, especially in the head and neck region, visceral organs, and lymphatic system abnormalities.
This procedure is usually performed by radiologists or specialists, with the assistance of ultrasound, computed tomography, or other imaging modalities to enhance sampling accuracy. Its core value lies in providing immediate pathological diagnosis, helping physicians distinguish benign from malignant lesions, and guiding treatment strategies.
FNAB is categorized into "open" and "closed" types: the closed type is suitable for superficial lesions, using a 0.6~0.9mm needle for direct puncture; the open type involves deep tissue sampling during surgery with imaging assistance. The mechanism involves aspirating cellular clusters with a puncture needle, followed by cytological staining (such as Papanicolaou stain) or rapid frozen section analysis, with interpretation by a pathologist based on cell morphology and arrangement.
This technique uses negative pressure suction to obtain sufficient cells for diagnosis. Recently, it has been combined with molecular biological techniques, such as liquid-based cytology, to improve the genetic assessment accuracy of malignant tumors.
Main indications include:
It is also applicable for fluid extraction (e.g., ascites, pleural effusion cytology) and the assessment of infectious lesions (e.g., tuberculous lymphadenitis).
The procedure involves: after local anesthesia, inserting a 22-25G needle into the lesion and repeatedly aspirating to obtain 3-5 cellular clusters, with a total operation time of approximately 15-30 minutes. Complex cases may require repeated punctures to improve diagnostic sensitivity.
Regarding dosage control, the number of punctures is adjusted based on lesion size; thyroid nodules typically undergo 3-5 aspirations, while deep lesions may require adjustment of needle angle and depth under imaging guidance.
The main advantages include:
In resource-limited settings, FNAB sensitivity can reach 85-95%, especially as the first-line examination for thyroid nodules.
Common side effects include:
Serious complications include pneumothorax (during thoracic lesion puncture), bleeding, or infection, with an incidence of less than 1%. Thyroid puncture may cause transient thyroid dysfunction, requiring close monitoring.
Contraindications include:
Preoperative instructions include stopping anticoagulants (such as aspirin) and signing informed consent. Post-procedure, avoid strenuous activity for 24 hours, and keep the puncture site dry.
Attention should be paid to interactions with anticoagulants, which should be temporarily discontinued 3-7 days before the procedure. The timing of radiotherapy should be coordinated with an oncologist to avoid affecting tissue structures. For imaging examinations, it is recommended to perform imaging-guided puncture first, followed by chemotherapy or targeted therapy to prevent tissue necrosis affecting diagnosis.
For thyroid nodules, FNAB has a sensitivity of up to 95% for malignant lesions and a specificity of about 85%. Large retrospective studies show that its accuracy is comparable to surgical biopsy but with a 60% lower complication risk.
In lymphoma assessment, combining flow cytometry can improve subtype classification accuracy. The American College of Radiology (ACR) lists it as the first-line diagnostic procedure for thyroid nodules.
Alternative methods include:
When choosing alternatives, considerations include diagnostic accuracy, patient tolerance, and resource availability. For high-risk lesions (e.g., suspected sarcoma), core needle biopsy is preferred to obtain complete tissue architecture.
It is recommended to wear clothing that allows easy exposure of the examination site and to inform the doctor in advance if there are coagulation abnormalities or if the patient is taking anticoagulants (such as aspirin). For suspected breast cancer lesions, avoid massaging or stimulating the breast before the procedure to prevent affecting the results. Bring relevant medical history documents on the day and sign the consent form on-site.
Is special care needed for mild swelling or bruising after the procedure?Mild swelling or bruising is common and usually resolves spontaneously within 1-2 weeks. Applying ice to the area within 24 hours after the procedure can reduce swelling, and strenuous activity should be avoided. If bleeding is heavy, pain worsens, or fever occurs, contact the medical team immediately for evaluation of possible infection or hematoma.
What should be done if the result shows "atypical cells"?Results indicating "atypical cells" suggest a risk of malignancy but are not definitive. The doctor usually recommends follow-up observation, additional imaging (such as ultrasound or CT), or an open biopsy to obtain more tissue samples for confirmation. Discussing risks and treatment options with a specialist is advised at this stage.
How long after the procedure can daily activities be resumed? What activities should be avoided?Most patients can resume normal activities after the procedure, but pressure or impact on the puncture site should be avoided. For example, patients with puncture sites on the neck should avoid tilting their head back. For breast procedures, avoid lifting heavy objects within 24 hours. If ultrasound-guided, hospitalization is usually unnecessary, but watch for signs of bleeding within 24 hours.
How accurate is fine needle aspiration diagnosis? When might repeat testing be necessary?The sensitivity of this test is approximately 85-95%. However, if tissue quantity is insufficient or cell morphology is atypical, additional imaging or repeat puncture may be needed. When pathology reports "indeterminate," clinical symptoms worsen, or the lesion continues to enlarge during follow-up, open biopsy or increased sampling may be recommended to improve accuracy.
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