INTRODUCTION
Fine needle aspiration biopsy (FNAB) is a relatively quick, simple, and safe method for obtaining tissue for diagnostic evaluation in cystic and solid lesions in the head and neck. This technique can be used to evaluate benign and malignant lesions and is typically one of the first steps in the workup of such masses. FNAB is a technique in which a fine needle is introduced into tissue, cells from that tissue are aspirated with or without negative pressure, and a diagnosis is rendered based on the cytologic evaluation of that tissue.
Information obtained from FNAB is reliable, as the positive and negative predictive values are greater than 90%, and overall diagnosis accuracy is between 75% and 90% or greater.
Numerous advantages of FNAB exist, including the ability to perform the procedure in office while avoiding costly hospital stays and fees for more invasive procedures. Studies have estimated that there is approximately $250 to $750 health care cost–related savings for every biopsy when performing FNAB over open surgical biopsy. FNAB is also typically cheaper than core needle biopsy, costing 6 to 7 times less than core needle biopsy. Patients also tend to be able to undergo biopsy sooner, have less time to diagnosis, and initiate treatment significantly sooner when having the workup start with FNAB over surgical alternatives.
Additionally, there are fewer postprocedure complications than with more invasive procedures. Many studies on FNAB note minimal complication rates, with the most common being minor hematoma without clinical significance. However, FNAB is not perfect. The results can be based on the experience of physician performing the procedure and the cytopathologist interpreting the tissue sample, as well as the tissue characteristics of the mass in question.
FNA in Head and Neck: Salivary, Lymph Nodes, Thyroid
Indications
FNAB within the head and neck is indicated in any patient with a suspicious lesion, including a nonpulsatile neck mass, salivary gland lesion, or thyroid nodule. These masses can be palpable for easy identification, but if an in-office ultrasound is available, this can be used to guide in-office biopsies of lesions that are not readily palpable. Using ultrasound for biopsy guidance can allow for enhanced visualization, avoidance of critical structures including vasculature and nerves, differentiation of solid versus cystic portions of the mass, and real-time monitoring of the biopsy procedure.
Contraindications
There are minimal absolute contraindications to FNAB. These include pulsatile lesions and those near the carotid bifurcation, as these lesions may cause significant bleeding in the neck. While bleeding can be a concern in those lesions, patients who are anticoagulated can still undergo FNAB with minimal risk of hematoma with proper compression of the biopsy site after the procedure.
Equipment
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Local anesthesia for injection. Sodium bicarbonate can be added to lidocaine to help ease the discomfort of injection of local anesthesia
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Skin prep
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Ultrasound
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Marking pen
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21- to 25-gauge needles that are length dependent on depth of mass. Typically, at least two or three needles will be required for multiple passes
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10-mL syringes (may use aspiration gun vs. figure control top syringes if negative pressure preferred). There needs to be the same number of syringes as needles
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30-mL container of CytoLyt
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Glass pathologic slides
Patient Preparation
All patients should receive counseling and sign an informed consent form prior to proceeding with FNAB, including a discussion of the risks, benefits, and alternatives of the procedure. Alternatives to FNAB include observation, core needle biopsy, or open excisional biopsy.
There are very few significant complications of FNAB. The most common risk is inadequate specimen requiring repeat biopsy. However, this outcome can be reduced significantly with rapid onsite evaluation by members of the cytopathology team. If there is inadequate specimen or if the result is nondiagnostic, FNAB may need to be repeated. Additional risks include pain and bleeding, although it is extremely rare for a clinically significant hematoma, even in patients on anticoagulation. ,
TECHNIQUE
The skin and subcutaneous tissues of the biopsy site are anesthetized with local anesthesia injection after cleansing the skin with 70% isopropyl alcohol wipe. Time is allowed for the anesthetic effect to be achieved.
The mass of concern is identified via ultrasound. The mass is localized on the screen and a marking pen is used to mark the location where the needle will enter the skin. This can be either directly over the mass, or at the edge of the mass to visualize the course of the needle with the probe in the coronal plane.
The syringe is filled with approximately 2 mL of air before beginning the procedure. The needle is inserted into the skin and advanced into the mass. The needle is advanced and retracted while applying negative pressure. Once sufficient passes have occurred, the negative pressure is released, and the needle is removed from the lesion to be prepared for cytologic evaluation. Releasing the negative pressure prevents the contents of the needle from being aspirated into the syringe, which would then make the transfer of the specimen to the slides difficult. The biopsy site is then dressed in a folded gauze and bandage once the procedure is complete.
Slide Preparation
The aspirated tissue is directly applied to a pathologic slide. This specimen is spread across the slide by placing another slide directly on top of the specimen and pulling the two slides apart. The specimen is then prepared for microscopic evaluation by either applying fixative spray or allowing the slide to air dry.
Additional tissue may remain in the needle or in the syringe. After the specimen is applied to the slide and the slide is prepared, the syringe is then used to aspirate and expel CytoLyt to ensure all cells are evaluated by the cytopathologist.
Having a cytopathologist or cytopathology tech available for rapid onsite evaluation while preparing the slides is helpful to ensure adequate specimen collection. This can significantly decrease the rate of nondiagnostic FNAB.
Ultrasound Guidance
As previously noted, ultrasound guidance can improve the procedure by allowing for real-time visualization of the procedure and allowing for enhanced visualization of the mass and surrounding critical structures. There are a few key steps to be successful at using the ultrasound for FNAB assistance.
First, the ultrasound machine must be turned on, properly calibrated, and functioning. Typically, the linear transducer is used to picture the structures, as this transducer allows for more concentration of the ultrasound beam, resulting in better visualization of superficial structures of the neck. Ultrasound gel is applied to the transducer, which is then applied to the neck in the target area. The mass is then identified and centered in the screen after scanning the neck in a systematic manner. The needle is then inserted into the skin, which corresponds to the mid-point of the transducer from the side to see the length of the needle as a hyperechoic linear structure, or perpendicular to the mass which will only show the tip with movement. It is advanced until it has entered the mass, then the biopsy is obtained via negative pressure aspiration with micro passes (this can also be performed without negative pressure).
DISCUSSION
Cystic Lesions
Cystic lesions are frequently seen in patients with neck masses. Recently there has been a significant rise in the rate of human papillomavirus–related oropharyngeal squamous cell carcinoma presenting as cystic masses. This disease tends to present as cystic neck metastasis, and should be first on the differential of a cystic lesion. Importantly, orders should be placed to evaluate for human papillomavirus–related disease under cytologic evaluation.
Additional diagnoses to consider with this presentation include metastatic nasopharyngeal carcinoma, metastatic thyroid carcinoma, branchial cleft cyst, thyroid and thyroglossal duct cysts, lymphatic malformations, and mucoepidermoid carcinoma of the salivary glands.
The approach to FNAB in these masses is generally the same as other lesions in the head and neck. However, special attention needs to be paid to the different components of the mass. Because the mass will have a majority cystic component, it is important to aspirate the cystic fluid but also to obtain tissue samples of solid portions of the mass. Only obtaining cystic fluid can decrease the diagnostic accuracy of the biopsy.
Thyroid
While some thyroid nodules are palpable and noted on physical examination, many are diagnosed incidentally. Many patients who are seen in an ENT clinic with concern for thyroid nodules have been previously evaluated, often by ultrasound. The American College of Radiology has developed a system for reporting findings of thyroid nodules on ultrasound and has recommendations on when to proceed with FNAB versus observation.
A set number of points are given for different findings in the following categories: composition, echogenicity, shape, margin, and echogenic foci. Classification ranges from TI-RADS1 to TI-RADS5 based on the number of points given. Patients with TR3-TR5 are recommended to undergo FNAB based on size of the nodule. Fig. 8.2 shows different examples of thyroid nodules on ultrasound and describes characteristic findings that are used to determine TIRADS scores.
