Fine Needle Aspiration Biopsy Technique and Specimen Handling

Determining Whether FNA Is Warranted

A patient presenting for FNA has almost certainly been referred by another physician. The patient’s clinical history should be reviewed when available, preferably before seeing the patient. A focused physical examination should be performed, confirming that the lesion is indeed palpable (and that FNA is appropriate) and ensuring that the correct site is aspirated. It is helpful to ask the patient to point to the mass. If the lesion is not palpable, image guidance may be needed for the biopsy. If the lesion cannot be safely sampled, it should not be aspirated. By reviewing the results of imaging studies and performing a focused physical examination, the operator should assess the lesion’s size and shape and its relationship to nearby structures like large blood vessels. Imaging studies document the internal qualities of the lesion (e.g., vascularity and the relative proportion of solid vs cystic areas) and its distance from the skin surface. This information guides the approach to the lesion (e.g., the length of needle to use). During the brief examination, the operator should inquire about a significant bleeding disorder, the use of anticoagulants, and sensitivities to any local anesthetics that may be used.

Obtaining Patient Consent

The consent process involves a detailed description of the procedure, including its purpose and potential complications, allowing for questions from the patient. Remind the patient that s/he may elect to stop the procedure at any time.

Sample Explanation of the Procedure

“Hello, Ms. Smith, I’m Dr. Ly from the Department of Pathology. I understand that Dr. Jones has sent you here for a fine needle aspiration of a mass in your neck. The goal is to obtain a diagnosis for the mass. Let me explain what the procedure involves. Feel free to ask questions at any time.

“I will use a very thin needle to take a sample of the mass. The needle is the same size or smaller than the ones used to draw blood. I will insert the needle into the mass and move the needle back and forth for about 15 to 20 seconds. I usually do this two or three times, which means two or three separate needlesticks. Sometimes I will sample a fourth time if it will help us get additional material to make a diagnosis. We will take a short break after the first or second needlestick while I quickly check how much material there is. The purpose is to ensure that we are obtaining enough material to make a diagnosis.

“Most patients feel a pinprick when the needle goes through the skin, like a blood draw, and while the needle is moving back and forth, most patients feel a dull pressure, pulling, or soreness. I can inject lidocaine into the skin over the lump if you like. It will be another small needle, and you may feel a burning sensation for a few seconds. If you cannot tolerate the procedure because of pain, I will stop and take the needle out.

“This procedure has a few minor risks that you should know about. Bleeding at the biopsy site can occur, but it is rare, occurring less than 1% of the time, even in patients taking blood thinners. After each needlestick, we will apply firm pressure with a gauze pad to minimize this. Infection can also occur, but this is even more unlikely. I clean the skin with alcohol before each needlestick to minimize the chance of infection.

“Do you understand the purpose of this procedure and the risks involved, and do you agree to the procedure? If so, please verify for me your full name and date of birth, and I’ll ask you to sign this consent form” (see Video 8.1 found on expertconsult.com ).

Readying the Equipment

The biopsy apparatus is assembled by loading a syringe onto the syringe holder and attaching a needle. Needles 22 gauge or smaller are considered “fine.” Commonly, 23- and 25-gauge needles measuring 1.0 to 1.5 inches long are used for palpable lesions. Larger-gauge needles (19 to 22 gauge) may be used for aspirating abdominal fat to test for amyloid deposition. The shortest needle that reaches the furthest area of the lesion from the skin should be chosen. Shorter needles (less than 1.0 inch long) are sufficient for small nodules close to the skin surface. Needles vary in design; those with beveled tips are preferred, but FNA does not require a specific needle type to be successful. Once set up, the needle cap is loosened, and the equipment placed within easy reach. If local anesthesia is to be given, it should be prepared at this time.

Because the sample must be prepared immediately before it dries/clots, several clean glass slides should be prelabeled with at least two patient identifiers (e.g., name, date of birth, medical record number), and alcohol slide fixative and a container filled with liquid transport medium should be at hand. These will be used to make smears, rinse the needle, and allocate material for special studies if necessary.

Positioning the Patient and Immobilizing the Lesion

The patient is positioned so that s/he is comfortable and the lesion can be palpated and immobilized. The patient should lie on their back when feasible; this is a safe position if there is a vasovagal response. Pillows, rolled towels, and foam shapes can be used for support. Changing the patient’s body position can dramatically affect the accessibility of the lesion. Breast masses, for example, are often best appreciated with the patient’s arm raised above the head. Neck nodules easily palpated with the patient in the sitting position may seem to recede into the soft tissues when the patient lies back. Becoming ambidextrous at FNA allows more flexibility in how the patient is positioned.

If the mass is deep to a band of skeletal muscle such as the sternocleidomastoid, position the patient such that the muscle is relaxed, securely grasp the muscle belly, and pull/push it aside. In addition to being painful, passing a needle through skeletal muscle clogs the needle with skeletal muscle and prevents adequate sampling. The exact method for stabilizing and immobilizing the mass varies and is influenced by factors such as the anatomic site, the size and mobility of the mass, and characteristics of the operator’s hands.

Once the method of immobilization and the needle trajectory have been determined, the skin is cleaned with an alcohol swab and local anesthesia injected (if desired). Buffered lidocaine solution tends to be less painful than unbuffered. Local anesthetic is advisable if the mass is tender to palpation or if the procedure involves a sensitive site like the nipple/areola. It is best not to inject so much local anesthetic that excessive skin swelling obscures the mass. This is particularly true with smaller nodules. One should target the sensory plexus, which is in the deep dermis. Encountering resistance while pushing the plunger is an indication that the needle tip is in the dermis, whereas no resistance is felt when injecting into the fatty hypodermis. Local anesthetics usually require a few minutes to take effect.

Sampling the Lesion

Once the mass is fixed with the non-aspirating hand, the skin is cleaned with an alcohol swab at the planned needle entry site (see Video 8.1 found on expertconsult.com ). The loosened needle cap is removed and the aspirating hand stabilized by resting the syringe barrel against the thumb or forefinger of the non-aspirating hand. This guards against any physiologic hand tremor and ensures precise needle placement but is not needed after insertion of the needle. The needle is inserted into the lesion, and the syringe plunger is pulled back to generate several cubic centimeters of vacuum. The vacuum is maintained during sampling and released just before the needle is removed from the patient. With a straight wrist, the needle is moved back and forth quickly and repeatedly in a sawing motion (“excursions”) for a dwell time no longer than 15 to 20 seconds (approximately 40 to 60 excursions) along the original needle trajectory, alternately advancing into the mass and withdrawing to a superficial location without exiting the patient. Slower needle action will yield less material. A shorter dwell time (e.g., 2–5 seconds) is recommended for vascular lesions such as thyroid nodules. Some practitioners also rotate the hand in a clockwise or counterclockwise fashion while it is moved within the lesion to achieve a “coring” effect, but this is not necessary. Each time the needle advances into the lesion, its cutting tip dislodges small tissue fragments; this cutting action is essential for successful FNA. Negative pressure alone without needle movement will not procure enough tissue for diagnosis in solid lesions. The vacuum in the syringe helps conduct the tissue fragments into the needle shaft and hub. A slight acceleration of the needle as it advances into the mass enhances the cutting action of the needle tip. Keeping the needle tip within the mass avoids diluting the specimen with adjacent non-lesional tissue. Material can be seen accumulating in the needle hub, although absence of visible material does not signify an inadequate sample. If blood rapidly enters the hub, withdraw the needle immediately, especially in a vascular site such as the thyroid gland.

There are nuances to the technique for different sites and types of lesions. Sampling with thinner needles (25 or 27 gauge) is preferred for vascular organs such as the thyroid, as well as for fibrous lesions such as fibroadenoma of the breast. When sampling a sclerotic lesion, the needle should be moved more vigorously.

To sample more of the mass with one needle pass, withdraw the needle tip to a superficial location while maintaining vacuum, then redirect it to a different area by changing the angle of entry. “Fanning” allows for sampling of a larger area: after each excursion, when the needle tip is in a superficial location, incrementally adjust its angle of entry slightly until the entire region of interest is sampled. Avoid changing direction when the needle is deep in the lesion because this causes tissue tearing and hemorrhage, which compromises the diagnostic yield of subsequent passes and is uncomfortable for the patient.

Remove the needle from the patient after the last excursion is completed or when material or blood is visible in the needle hub, which can occur in less than 15 seconds. Withdraw the needle from the patient in a controlled manner and only after release of the vacuum in the syringe. Failure to release suction before withdrawing the needle from the patient pulls the aspirated material into the barrel of the syringe, making it difficult to expel for smear preparation. Pressure to the site is applied immediately with gauze to minimize bleeding. The patient or an assistant should perform this step because the operator needs to prepare the sample immediately.

An FNA procedure typically involves inserting the needle into the mass two or three times (“passes”) to obtain several samples. The center of the mass is often sampled on the first needle pass with the needle approximately perpendicular to the skin. Other areas of the mass are sampled on subsequent passes, especially if the initial material is necrotic, cystic, or otherwise nondiagnostic. Sampling the mass along its long axis tends to yield more cellular specimens compared with moving the needle along the short axis.

In most cases, an FNA should not be performed on a given site more than three to four times at one clinic visit. Repeated biopsies increase tissue hemorrhage, reducing diagnostic yield. It is better to have the patient return in several days for a repeat FNA.