Fine-needle aspiration (FNA) is a diagnostic procedure used to investigate lumps or masses. In this technique, a thin (23–25 gauge (0.52 to 0.64 mm outer diameter)), hollow needle is inserted into the mass for sampling of cells that, after being stained, are examined under a microscope (biopsy). The sampling and biopsy considered together are called fine-needle aspiration biopsy (FNAB) or fine-needle aspiration cytology (FNAC) (the latter to emphasize that any aspiration biopsy involves cytopathology, not histopathology). Fine-needle aspiration biopsies are very safe minor surgical procedures. Often, a major surgical (excisional or open) biopsy can be avoided by performing a needle aspiration biopsy instead, eliminating the need for hospitalization. In 1981, the first fine-needle aspiration biopsy in the United States was done at Maimonides Medical Center. Today, this procedure is widely used in the diagnosis of cancer and inflammatory conditions. Fine needle aspiration is generally considered a safe procedure. Complications are infrequent.
Aspiration is safer and far less traumatic than an open biopsy; complications beyond bruising and soreness are rare. However, the few problematic cells can be too few (inconclusive) or missed entirely (a false negative).
Medical uses
This type of sampling is performed for one of two reasons: A biopsy is performed on a lump or a tissue mass when its nature is in question. For known tumors, this biopsy is performed to assess the effect of treatment or to obtain tissue for special studies.
When the lump can be felt, the biopsy is usually performed by a cytopathologist or a surgeon. In this case, the procedure is usually short and simple. Otherwise, it may be performed by an interventional radiologist, a doctor with training in performing such biopsies under x-ray or ultrasound guidance. In this case, the procedure may require more extensive preparation and take more time to perform.
Also, fine-needle aspiration is the main method used for chorionic villus sampling, as well as for many types of body fluid sampling.
It is also used for ultrasound-guided aspiration of breast abscess, of breast cysts, and of seromas.
Preparation
No aspirin or non-steroidal anti-inflammatory medications (e.g., ibuprofen, naproxen) for one week before the procedure No food a few hours before the procedure Routine blood tests (including clotting profile) must be completed two weeks before the biopsy. Suspension of anticoagulants (blood thinners) Antibiotic prophylaxis may be instituted.
Before the procedure is started, vital signs (pulse, blood pressure, temperature, etc.) may be taken. Then, depending on the nature of the biopsy, an intravenous line may be placed. Very anxious patients can be sedated through this line, or oral medication (Valium) may be prescribed.
Procedure
The skin above the area to be biopsied is swabbed with an antiseptic solution and draped with sterile surgical towels. The skin, underlying fat, and muscle may be numbed with a local anesthetic, although this is often not necessary with superficial masses. After locating the mass for biopsy, using x-rays or palpation, a special needle of very fine diameter is passed into the mass. The needle may be inserted and withdrawn several times. There are many reasons for this: One needle may be used as a guide, with the other needles placed along it to achieve a more precise position. Sometimes, several passes may be needed to obtain enough cells for the intricate tests which the cytopathologists perform. After the needles are placed into the mass, cells are withdrawn by aspiration with a syringe and spread on a glass slide. The patient's vital signs are taken again, and the patient is removed to an observation area for three to five hours. For biopsies in the breast, ultrasound-guided fine-needle biopsy is the most common. The biopsy is advised.
Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) EUS-FNA is a minimally invasive procedure for acquiring biopsies in gastric regions that are hard to reach otherwise (e.g. the pancreas). Endoscopic ultrasound EUS-FNA of cystic lesions, followed by liquid cell analysis, has been used as a diagnostic tool for differentiating benign, potentially malignant, and malignant pancreatic cysts. 'Through-the-needle' cytologic brushes have been developed for increasing the cellular content in the aspirates.
Rapid on-site evaluation (ROSE)