Fine-Needle Aspiration

Fine-Needle Aspiration

John J. Buchino, M.D.

Robert F. Debski, M.D.

Fine-needle aspiration (FNA) was first reported in the early 1930s by Martin and Ellis (1) and Stewart (2), but the procedure did not gain widespread acceptance until after Zajicek published his monograph in 1974 (3). Although several studies and monographs have established the usefulness of FNA in pediatrics, many pediatric centers have been slow to adopt this invaluable technique. Those that have adopted this technique, however, have found it to be a relatively easy, low-cost diagnostic procedure that can provide a great deal of information (4). Several important advantages of FNA are listed in Table 1B-1. It is important that clinicians recognize that FNA is most applicable in discrete mass lesions, generally not in diffuse processes such as cellulitis or a pulmonary infiltrate. Typical indications for the use of FNA in children are summarized in Table 1B-2. For several reasons (given below), it is strongly recommended that a pathologist perform FNA of all palpable lesions and that a pathologist should be present to assist when a radiologist performs an image-guided FNA of deep-seated lesions, regardless of image modality (CT, MRI, ultrasound, etc). Thereupon, the pathologist is able to obtain an accurate history and observe the exact size and location of the lesion. The person performing the aspiration is best able to evaluate whether the lesion has been penetrated. As one gains experience, the texture of the lesion and consistency of the aspirated material assist in the formulation of a differential diagnosis. The pathologist is also best able to prepare the smears and triage the aspirate material for ancillary studies.

The standard equipment required for FNA is listed in Table 1B-3. If need be, the equipment and supplies can easily be carried in a phlebotomy tray to the patient’s bedside or, preferably, to a treatment room. Outpatient FNA should be performed in a clinic or hospital-based setting with adequate room for the patient, parents, and assistants, as well as the pathologist. An adjacent area or an appropriate cart for rapid staining and microscopic evaluation is highly desirable. Although untoward complications are extremely rare with the aspiration of superficial lesions, the procedure room should be equipped to handle emergencies, as with any other area in which clinical procedures are carried out.

In general, relatively few complications are associated with FNA. The most common is bruising or swelling at the FNA site. Inadvertent puncture of a vessel may result in a small hematoma. Nevertheless, a history of a possible bleeding diathesis should always be obtained. A vasovagal response or light-headedness may occur in a small percentage of patients (be aware, parents may also feel faint when observing the procedure). A pneumothorax is possible when a chest wall lesion or a lesion in the supraclavicular space is aspirated. Seeding of tumor in the needle tract, while reported, is a markedly rare occurrence (5).

The FNA technique is outlined in Figure 1B-1. This is essentially the same as the technique used for adults. Of note, the use of an FNA syringe holder (i.e., “aspirator” or “aspiration gun”) and the specific type (i.e., “pistol-grip” or “pencil-grip” syringe holder) are optional. In children, the standard size of needle for a superficial lesion is usually 1 inch, 23 gauge. A 23-gauge needle recovers adequate material for diagnosis in more than 90% of cases and is unlikely to cause any significant organ or vessel trauma. A 22-gauge needle may facilitate the drainage of purulent material but should not be used in regions where a major vessel may be sheared (e.g., near the carotid artery). The pathologist must also be mindful of spatial differences, such as decreased chest wall thickness in infants and small children.

When performing an FNA on an infant or child, adequate control of the patient is imperative. Nobody wants to attempt the aspiration of a moving target. Thus, a skilled assistant, such as a nurse or pathology assistant, is invaluable in this situation. Since the procedure is relatively brief, the assistant is usually able to hold and control infants less than 1 year of age in the desired position. Children older than 6 years can generally cooperate well when talked through the procedure. Children between 12 months and 6 years, however, can be difficult because of their lack of comprehension of what is happening and their strength. Sedation should be used whenever possible. Most tertiary care pediatric services now have sedation teams that are adept at sedating children for short procedures. The choice of sedatives may
vary and is somewhat dependent on the personal preference of the anesthesiologist and/or the pathologist. When sedation is used, the child must be monitored in the appropriate fashion. If sedation is not available, a papoose wrap may be employed to immobilize the child. Also, use a local anesthetic whenever possible. The only exceptions to the use of a local anesthetic are a known allergy and a lesion so small that the injected anesthetic will make it difficult to palpate and properly sample the lesion.

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Sep 23, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Fine-Needle Aspiration
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