Percutaneous fine-needle aspiration biopsy

See also: Minor Surgery > Best Treatment > Therapeutic skills > Fine-needle aspiration biopsy (FNAB)

For diagnostic purposes, certain cystic and solid masses can be aspirated and the obtained aspirate examined microscopically. Needle biopsies have been used to differentiate benign and malignant lesions since the late 1800s. Fine-needle aspiration biopsy (FNAB) was pioneered in Scandinavia as a simple, fast, and inexpensive biopsy technique. At present, percutaneous FNAB is still a relatively safe and painless method of obtaining small cores of tissue for cytopathological examination which can be carried out in out-patients. In most cases, however, cytology should be used in conjunction with other preoperative investigative methods.

Generally, the FNAB should be performed after radiological examinations (e.g. mammography) because the resultant haematoma could mask an underlying abnormality. This can also be done under ultrasound guidance if lumps are small or close to the arteries (Goldberg A, Stansby G (eds), 2005) .

FNAB can be performed as a valuable technique of sampling solid and cystic masses in a variety of anatomic sites, including the breast and thyroid, lymph nodes, and other superficial soft tissue lesions (Goldberg A, Stansby G (eds), 2005) (Chen H, Sonnenday CJ, Lillemoe KD (eds), 2000) (Cracknell ID, Mead MG, 1997) .
For tumours of these sites the overall diagnostic accuracy is greater than 70%, and the overall sensitivity for detecting malignancy by FNAB is between 80% and 85%. However, in case of thyroid nodules, FNAB cannot differentiate between follicular adenomas and follicular carcinomas (Goldberg A, Stansby G (eds), 2005) . Multiple thyroid nodules are usually benign, whereas solitary nodules may be malignant. The greatest advantages of FNAB is in the elimination of some open biopsies.

Indications

1. Presence of a palpable suspicious mass in the breast: evaluation of the mass; aspiration of breast cysts; differentiation of benign from malignant lesions
2. Thyroid nodule: evaluation of palpable masses; differentiation of benign from malignant thyroid lesions; fine-needle aspiration (if necessary under ultrasound guidance) should be the first-line investigation of any thyroid lump
3. Clinically suspicious lymph node or group of nodes (note: suspected granulomatous infection of a node – fungal or mycobacterial – does not contraindicate FNAB)
4. Any palpable, superficial, non-pulsating mass

Contraindications

1. Generally: none
2. Relative: unskilled clinician or absence of a cytopathologist
3. Sites of active pyogenic infection
4. Non-palpable lesions

The procedure for aspirating breast or thyroid nodules is generally the same. The nodule can be punctured, after appropriate skin disinfection, with a fine needle attached to a syringe. During aspiration, the nodule is fixed between two fingers (Fig. 1). The aspirate of a solid mass (only this within the lumen of the needle) is placed on a slide for Papanicolaou or H&E (haematoxylin and eosin) staining and evaluation. Smears that do not contain cellular material are unsatisfactory. If a cyst is aspirated and fluid is obtained, it should be sent for cytology. Proper preparation of the smears is as important as the aspiration technique itself. Furthermore, a cytopathologist experienced in the interpretation of FNAB specimens is required for the best diagnostic results.

The patient should understand, however, that non-diagnostic results may occur commonly and may require repeat FNAB or even open biopsy. Moreover, false-negative and false-positive results are possible (Pfenninger JL, Fowler GC (eds), 2003) .

Complications

There is no direct evidence that FNAB causes tumour dissemination. Serious haemorrhage at the site of biopsy is also uncommon. FNAB may be performed safely in patients on anticoagulants provided the test results are in the therapeutic range. Afterwards the biopsy site should be adequately compressed to avoid haematoma. Infection is extremely rare in FNAB. It may be performed in all but the most severely immunocompromised patients (Pfenninger JL, Fowler GC (eds), 2003) .