Fine-Needle Aspiration of Neck Masses

Updated: Sep 25, 2018
  • Author: Jonas T Johnson, MD, FACS; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Overview

Overview

Clinical evaluation of a solitary neck mass can be difficult because of the extensive differential diagnoses (listed below). In certain infections and neoplasms, open biopsy can lead to complications in further treatment once the etiology of the neck mass is determined. Thoughtful evaluation of the workup of a neck mass is of utmost importance, and fine needle aspiration (FNA) can often provide a timely diagnosis with less morbidity to the patient and decreased cost compared to open biopsy.

When evaluating a patient with a solitary neck mass, age of the patient is an important factor in determining the differential diagnoses. Individuals younger than 40 years are overwhelmingly diagnosed with benign processes such as congenital and inflammatory lesions. In patients older than 40 years, the differential diagnoses shift, as more than 60% of lesions are associated with malignancy. 

In the era of increasing incidence of human papilloma virus (HPV)-associated oropharyngeal head and neck squamous cell carcinoma (OPHNSCC), clinicians should not exclude the possibility of malignancy in non-smoker/non-drinker patients. [1]  The incidence of HPV-positive OPHNSCC has more than doubled [2, 3]  with a rate rising so rapidly that HPV-positive OPHNSCC is estimated to exceed the incidence of HPV-positive uterine cervical cancer by 2020. [3, 4]  Often these patients present with the sole symptom of neck mass that on imaging can appear cystic and be mistaken for a branchial cleft cyst resulting in delayed diagnosis. For patients with HNSCC, a delay of just 2 months has been associated with worse functional outcomes, lower quality of life, and cancer recurrence. [5, 6, 7]  In adult patients, a cystic neck mass should not be presumed to be benign disease, and therefore evaluation with FNA and/or additional imaging studies should be pursued until a diagnosis is obtained. [1]

Differential diagnoses of neck masses

See the list below:

  • Metastatic

    • Squamous cell carcinoma (SCC)

    • Adenocarcinoma (most commonly from salivary gland origin)

    • All other primary sites imaginable have been reported.

  • Primary neck tumors

    • Thyroid

    • Lymphoma

    • Salivary gland neoplasia

    • Paraganglioma

  • Congenital

    • Thyroglossal duct cyst

    • Branchial cleft cyst

    • Hemangioma

    • Dermoid cyst

    • Ectopic thyroid

    • Thymic cyst

  • Inflammatory

    • Lymphadenopathy (may be viral or bacterial)

    • Sarcoid

    • Tuberculosis

    • Cat scratch

    • Sialadenitis

See 10 Patients with Neck Masses: Identifying Malignant versus Benign, a Critical Images slideshow, to help identify several types of masses.

Evaluation of a patient with a neck mass should always begin with a thorough history, followed by a complete head and neck examination. Associated symptoms that should alert the clinician for malignancy include hoarseness, otalgia, unilateral hearing loss, hemoptysis, weight loss, dysphagia, and odynophagia. A history of fever, night sweats, and weight loss may suggest lymphoma. Physical exam findings of overlying skin ulceration, firmness, or size greater than 1.5 cm are physical exam findings more suggestive of malignancy. [1, 8]

If the history and physical examination do not explain the neck mass, a fine-needle aspiration (FNA) of the neck mass may be performed. The results of the FNA may allow the physician to focus further testing. For instance, if the mass is found to be a metastatic squamous carcinoma, a thorough examination of the upper aerodigestive tract is warranted. Additionally, imaging is recommended prior to FNA if there is a suspected vascular lesion (palpable thrill or auscultation of bruit on physical exam).

FNA for cytologic evaluation of a neck mass was first reported by Kun in 1847. The procedure did not gain wide acceptance in medicine at that time, but in the 1930s, Memorial Sloan Kettering rediscovered the utility of needle biopsy for evaluation of head and neck masses. At that time, use of large-bore needles led to frequent complications, one of which was occasional seeding of the tumor along the biopsy tract. [9, 10] The frequent morbidity associated with this procedure prevented widespread acceptance of this technique in other centers in America. In the 1970s, Swedish physicians demonstrated excellent results in cytologic examination of metastatic neck lesions with the use of FNA leading to a resurgence of this technique. [11]  Since then, FNA of solitary neck masses has become a well-accepted, safe, and cost-effective procedure in the diagnosis of neck masses.

FNA allows the pathologist to see the cells aspirated from the lesion. In contrast to large bore needle biopsy techniques, FNA does not allow evaluation of cell morphology. In some instances, aspirated cells can be evaluated by flow cytometry or with immunologic markers. In every circumstance, FNA is a test and should be interpreted with the entire clinical circumstances. False-negative and false-positive FNA results are reported in almost every series. Therefore, reliance upon FNA findings at the expense of clinical, radiographic, or other findings is unsafe. [12]

Advantages over open biopsy

FNA has several advantages over open biopsy for both the physician and the patient. FNA can be performed with or without image guidance. Image-guided tissue sampling can be performed with ultrasound or CT. FNA can be performed quickly and with minimal setup time, even with ultrasound guidance. CT-guided FNA is more time consuming, but can be useful for deep targets (masticator space, deep lobe of parotid, pterygopalatine fossa). CT-guided FNA may require evaluation of renal function if intravenous contrast dye is used. Ultrasound-guided FNA also may be more advantageous in the pediatric population where concern for ionizing radiation exposure is higher. The American Thyroid Association recommends ultrasound guidance for FNA of nodules with higher liklihood of nondiagnostic cytology ( >25–50% cystic component) or sampling error (difficult to palpate). [13]

FNA is more convenient for patients and their families compared to open biopsy. The procedure requires only an office visit with minimal loss of time from work. On the other hand, excisional biopsy often requires time off from work, preoperative blood tests, and often, radiographic and cardiac testing. Furthermore, surgery exposes patients to the risks of anesthesia, postoperative infection, and the possibility of tumor seeding (see below). A percentage of patients may require overnight admission to the hospital and extra time away from work.

Open biopsy may interfere with further treatment. Incorrectly placed biopsy incisions may make subsequent neck dissection or excision difficult. In 1991, Birchall and colleagues demonstrated that 6 of 10 patients undergoing excisional biopsy of masses experienced complications in relation to the biopsy. [14] These complications included compromise of later tumor resection, the necessity for excision of extra skin and adjacent soft tissue, and local recurrence in the neck wound after surgery.

In today's economic environment, cost savings is an important consideration in medicine. The cost of FNA in the office varies from $75 to $350 depending on the study source and whether or not the pathology fees are included. In contrast, the cost of an excisional biopsy ranges from $1200 to $2500. The cost is even higher if a hospital stay is required.

Limitations of fine-needle aspiration

Fine-needle aspiration (FNA) for head and neck masses has several limitations. Failure to establish an accurate diagnosis may be because of sampling error. In these circumstances, repeat aspiration is suggested, and excisional biopsy may be considered. Personnel responsible for handling, processing (experienced cytotechnologist), and reading (cytopathologist) FNA samples must be well trained. Interobserver variability must be minimized. The accuracy of FNA varies with report and according to the tissues sampled (see specific examples below).

The diagnostic accuracy following aspiration of a cystic mass may be especially suspect because of the potential to aspirate acellular material. [15]  In fact, the sensitivity of FNA is lower in cystic cervical neck masses compared to solid neck masses (73% and 90% respectively). [16, 17]  Good evidence currently suggests that the best results are achieved when FNA is accomplished using ultrasonographic or CT guidance to improve sampling accuracy. [18]  Either modality allows more precise localization of lesions and may facilitate more accurate positioning of the needle to aspirate the capsule in lesions with central necrosis. Accuracy is further enhanced by including a cytologist at the chairside to stain and preview the slides before the procedure is terminated. This also offers the potential to obtain extra material for flow cytometry when a lymphoma is suspected.

If any questions exist regarding interpretation of the aspirate, decisions on further therapy (eg, surgery, radiation, chemotherapy) should be deferred until the mass is accurately diagnosed. Finally, using FNA under the appropriate conditions is important. FNA complements clinical diagnosis and should not be considered a substitute for a thorough history and physical examination.

Relevant Anatomy

The neck is the part of the body that separates the head from the torso. The Latin-derived term cervical means "of the neck." The neck supports the weight of the head and is highly flexible, allowing the head to turn and flex in different directions.

The midline in front of the neck has a prominence of the thyroid cartilage termed the laryngeal prominence, or the so-called "Adam's apple." Between the Adam’s apple and the chin, the hyoid bone can be felt; below the thyroid cartilage, a further ring that can be felt in the midline is the cricoid cartilage. Between the cricoid cartilage and the suprasternal notch, the trachea and isthmus of the thyroid gland can be felt.

The quadrangular area is on the side of the neck and is bounded superiorly by the lower border of the body of the mandible and the mastoid process, inferiorly by the clavicle, anteriorly by a midline in front of the neck, and posteriorly by the trapezius muscle.

The image below depicts the anterior cervical muscles.

Anterior cervical muscles. Anterior cervical muscles.

For more information about the relevant anatomy, see Neck Anatomy.

General results of fine-needle aspiration

Interest in the use of fine-needle aspiration (FNA) in the diagnosis of neck masses has increased. Scandinavian success with FNA has been replicated by several large American studies for the head and neck. In 1982, Frable and Frable reviewed the success of FNA in 567 patients with neck masses. [19] Since then, multiple reports of experience with FNA in the diagnosis of head and neck lesions have been published. Sensitivity and specificity rates are approximately 85-90%. This means the incidence of false-negative and false-positive results range from 10-15%. FNA is not a substitute for excisional biopsy but should be considered an additional diagnostic tool to be used concurrently with patient history, physical findings, and laboratory tests.

Fine-needle aspiration in pediatric patients

Neck masses in children differ from those in adults. Children are far more likely than adults to have reactive lymphadenopathy. Primary or secondary malignant involvement is rare in children.

Unfortunately, the literature on FNA in children is limited by small study size and varying results. Stevens et al report a meta-analysis of FNA biopsy in pediatric thyroid nodules. [20] They conclude it is a sensitive test and useful for excluding malignancy. A recent small study of 18 pediatric patients with cervical lymphadenopathy found FNA biopsy to have 100% sensitivity, 93% positive predictive value, and 94.5% accuracy for distinguishing malignancy from benign lymphadenopathy. [21]

FNA for evaluation of neoplastic etiology of neck mass 

Although fine-needle aspiration (FNA) may not be the method of choice for all neck masses, studies demonstrate a specific advantage of FNA for the diagnosis of several specific disease entities. FNA is useful for the diagnosis of metastatic squamous cell carcinoma, thyroid carcinoma, and lymphoma. FNA showed an overall accuracy rate of 93.1% (range, 73.3%–98.0%), overall sensitivity of 89.6%; specificity, 96.5%; positive predictive value, 96.2%; and negative predictive value, 90.3%. Of the anatomic subsites within the head and neck, thyroid and salivary gland location had lower sensitivity (81.1% and 82.5%, respectively) and lymph node FNA had a higher sensitivity (92.5%). [22]

Metastatic squamous cell carcinoma

In a study of metastatic squamous cell carcinoma of the neck subsequently treated by neck dissection, Knappe et al [23] found that ultrasound-guided FNA had a sensitivity of 89%, specificity of 98%, and accuracy of 94%. In the event of the unknown primary squamous cell carcinoma of the head and neck, the predictive power of FNA allows physicians to narrow the search for the primary tumor. Furthermore, FNA can be a powerful tool for diagnosing cervical recurrence of head and neck squamous cell carcinomas without the financial costs and the morbidity of excisional biopsy. 

FNA biopsy for diagnosis of squamous cell carcinoma may have lower sensitivity in the event of a cystic mass or previous neck irradiation. Chan and Chan note that in patients who previously received radiation, the sensitivity of FNA was only 40%, compared with 82% in patients without prior neck irradiation. [24]  Gourin and Johnson report FNA results in 12 patients with cystic metastasis. False-negative aspirates were encountered in 5 (42%) patients. [15]  In each case, the diagnosis was made by excisional biopsy. The presence of a thick-walled cyst should raise clinical concern for this entity.

More recently, FNA has been useful for detection of squamous cell carcinoma related to human papillomavirus (HPV). In a review of 70 patients who underwent FNA for squamous cell carcinoma, two thirds of the FNA specimens contained adequate DNA for molecular detection of HPV-related disease. [25]  The College of American Pathologists (CAP) recommend high-risk HPV staining be performed on all patients with newly diagnosed oropharyngeal squamous cell carcinoma and p16 can be used as a surrogate marker. Interpretation of p16 staining has been controversial, although the accepted definition of a positive result is >70% cytoplasmic and nuclear staining. [26]  There are no well-established guidelines for p16 positivity from FNA/cell blocks. Reported positive results range from 10% to 50% with some authors citing that at least 15% positivity is needed, a number that correlates with high-risk HPV RNA in situ. [26, 27, 28, 29]  Other studies stress that p16 positivity only be evaluated in viable tumor cells. [26]

Other markers identified on ancillary testing may be of use when analyzing FNA samples. Although evidence for prognostic utility of program death  ligand 1(PD-L1) expression in HNSCC is unclear at this time, it has been shown to be of prognostic utility in certain lung malignancies.55 Evaluation of FNA aspirates for PD-L1 expression showed high concordance with open biopsy and core biopsy specimens. [30, 31]  

Thyroid Carcinoma

The prevalence of thyroid nodules detectable by ultrasound may approach 60–70% in the population. [32, 33, 34] Incidence varies by age and method of detection. Incidence of carcinoma in thyroid nodules is less than 10% in most populations. Many studies have examined the use of FNA in the diagnosis of masses suspicious for thyroid malignancies. A study of FNA biopsy in nearly 2000 patients at the Mayo Clinic showed a 97% positive predictive value and a 92% negative predictive value for malignancy. [34] Other reports support these data. [32, 35] While thyroid nodules larger than 4 cm are more likely to be malignant, [33] it is unclear whether FNA is less accurate for nodules of this size. A large study in more than 1000 patients showed no difference in sensitivity, specificity, or positive predictive value of FNA for nodules larger than 4 cm compared with those smaller than 4 cm; negative predictive value was improved for nodules larger than 4 cm. [36]

While papillary thyroid carcinoma can often be diagnosed with FNA based on classic cytologic features, [33] follicular adenoma is difficult or impossible to distinguish from follicular carcinoma in most aspirates. The difficulty in distinguishing benign from malignant has led to the term follicular neoplasm. Because of the difficulty in differentiating follicular adenoma from well-differentiated follicular carcinoma with FNA, the presence of a follicular neoplasm with FNA is an indication for thyroid surgery. Recent investigations report that the use of molecular markers such as BRAF, galectin-3, HBME-1, PAX-8-PPARγ, RAS, and RET/PRC are gaining increasing clinical usefulness. [37, 38, 33, 39, 40]

Lymphoma

When cytologic evaluation suggests a lymphoid lesion, further study may be essential to rule out lymphoma. Although FNA is 98% specific for the absence of tumor and 95% sensitive for the presence of tumor in most neck masses, improper diagnosis may be encountered when trying to distinguish lymphoma from reactive lymphadenitis.The accurate cellular diagnosis of a specific lymphoma depends on changes in lymph node architecture, which requires morphologic examination of the entire node. However, when the previous cytoarchitecture of a lymphoma specimen is known, FNA is reliable in predicting recurrence.

Some reports have suggested that Hodgkin lymphoma can be accurately diagnosed by FNA. Hodgkin lymphoma is suggested by the presence of Reed–Sternberg cells in the setting of numerous lymphocytes on FNA. The role of FNA in the diagnosis of non-Hodgkin lymphoma (NHL) is controversial. The diagnostic yield of FNA is low because differentiating non-Hodgkin lymphoma from lymphocytic thyroiditis and anaplastic thyroid carcinoma is difficult. Studies that combine FNA with flow cytometry and immunohistochemistry may increase the accuracy of lymphoma diagnosis without the need for excisional biopsies. The National Comprehensive Cancer Network (NCCN) guidelines state that with regard to most NHL entities, FNA or core biopsy is insufficient for initial diagnosis due to lack of accurate histologic grading for entities such as follicular lymphoma. [41]

Flow cytometry uses a beam of laser light to identify cell surface antigens. Tagged antibodies bind to cell surface antigens on lymphocytes, allowing the identification of non-Hodgkin lymphoma. Recently, flow cytometry has been used to help diagnose pathology on FNA. In a 10-year study of more than 500 patients by Savage and colleagues, flow cytometry was performed on FNA specimens to differentiate lymphoma from reactive lymphadenopathy, with results compared to histologic diagnosis from excisional biopsy or to prolonged follow up. The authors noted that flow cytometry had an accuracy of 88.4%, sensitivity of 85.8%, and specificity of 92.9%. [42]

Salivary gland carcinoma

Use of FNA for isolated salivary gland masses is broadly accepted. Nevertheless, surgeons are cautioned to interpret the result of FNA within the context of the clinical situation. Salivary gland cytology is a known challenge due to frequent morphologic overlap between tumor types. [43]  Both false-negative and false-positive results are encountered. Interpretation of salivary gland pathology is difficult (the most common tumors are "pleomorphic" adenoma) and requires greater experience than the interpretation of some other neck masses.

In 2012, Tryggvason et al evaluated FNA biopsy in 543 patients with salivary gland masses, the majority involving the parotid gland, finding a sensitivity of 85.7% and specificity of 99.5% for identification of the final histologic diagnosis following surgical resection. [44]  Positive predictive value for malignancy was more than 98%, while negative predictive value was 94.3%. In another 2012 study including 249 patients with parotid masses, FNA was found to be only 80% sensitive and 89.5% specific for the detection of malignancy. [45]   

Immunohistochemical and genetic characterization of salivary gland neoplasms has increased, and ancillary testing may be quite useful in narrowing the differential in challenging cases. With the exception of special stains for microbiology, ancillary testing is not indicated in nonneoplastic salivary gland FNA results. If FNA is suspicious for a neoplastic process, ancillary testing may be useful for entities that have nonspecific or overlapping morphology. [43]  Immunohistochemistry, FISH, and sequence-based methods can be performed on cytologic materials. For example, 70% of pleomorphic adenomas have recurrent genetic alterations with the majority being translocation or intrachromosal rearrangements of the PLAG1 gene locus (50–60%) and HMAG2 gene locus(10–20%). [46, 47, 48, 49]  Mucoepidermoid carcinoma can present a diagnostic challenge depending on tumor grade and sampling error. Ancillary testing with molecular confirmation of the MAML2 gene rearrangement offers definitive diagnosis. [43]

FNA alone may not be sufficient to rule out salivary malignancies and that further clinical evaluation, including surgical resection, may be necessary. Most reports acknowledge a low but important incidence of false-positive aspirates. When clinical suspicion warrants it, further sampling (eg, excisional biopsy) is appropriate.

FNA for evaluation of neck mass from infectious etiology

FNA is routinely used for the histologic diagnosis of isolated neoplastic neck masses. However, use of FNA in the diagnosis of inflammatory lesions has been limited. FNA could likely be used to isolate individual organisms or at least allow for the culture of an offending organism. An array of case reports and case series has demonstrated a use for FNA in the diagnosis of infectious diseases of the neck. A few of the causes identified include Staphylococcus aureus, Escherichia coli, and Bacteroides fragilis; Cryptococcus, Mycobacterium, Coccidioides, Bacteroides, Streptococcus, Haemophilus, Pseudomonas, and Citrobacter species; and Cytomegalovirus infection, syphilis, and actinomycosis.

Tuberculous lymphadenitis is a common extrapulmonary presentation that may manifest as a neck mass. FNA specimens have cytologic evidence consistent with tuberculosis, including granulomatous inflammation and/or caseation necrosis. Multiple studies have demonstrated greater than 90% accuracy in diagnosis of tuberculous lymphadenitis with FNA. [50, 51, 52]  However, the positivity rate of mycobacterial culture from FNA reported in the literature ranges from 10% to 70%. Real time polymerase chain reaction (PCR) on aspirate materials, specifically for the IS6110 sequence, is a a useful molecular  ancillary test used for diagnois of  tuberculosis lymphadenitis. [53, 54]

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Indications

If the physical examination does not explain the neck mass, a fine-needle aspiration (FNA) of the neck mass should be considered.

If the mass is believed to be a metastatic lesion, careful examination of the entire upper aerodigestive tract (eg, nasopharynx, larynx, hypopharynx) is warranted.

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Contraindications

Fine-needle aspiration (FNA) carries almost no absolute contraindications. If the physician is concerned about proximity to vital structures, guidance with computed tomography (CT) or ultrasonography (US) is available.

Coagulopathy is of some concern. As most FNA procedures are elective, efforts should be directed at correction of the coagulation defect. In patients who are anticoagulated, some reversal of the drug is usually done before the procedure.

In all cases, proper compression after the procedure is completed is essential.

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Equipment

Equipment necessary for conducting fine-needle aspiration (FNA) includes the following:

  • A 21-gauge needle is commonly used. Larger needles may be used, but they involve a higher risk of complication and may result in contaminating the specimen with red blood cells.

  • Various custom syringe holders are currently available in the marketplace.

  • Use of topical or infiltrative anesthesia is encouraged. It is not necessary to infiltrate directly into the target mass, but the overlying skin can be anesthetized to afford improved comfort.

  • Ultrasound equipment*

*optional but can be useful in certain circumstances

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Positioning

An important step in any procedure, including fine-needle aspiration (FNA), is patient positioning. The patient is positioned to allow the most optimal digital palpation of the mass.

In the event the mass is not easily palpable, the physician should call upon either US or CT to improve diagnostic accuracy.

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Technique

Fine-needle aspiration (FNA) is a simple office procedure that requires a few minutes to complete. It is ideal to have the cytotechnologist and pathologist available at the time of the aspiration. This allows an immediate assessment of the adequacy of the specimen, and if insufficient cells have been obtained, the aspirate can be repeated. Sometimes the diagnosis can be made immediately. Consultation with a cytopathologist is useful to determine appropriate collection media. For example, roswell park memorial institute (RPMI) collection media is used for collection for lymphoma evaluation. Additionally, a portion of cytology should be submitted in a fixative solution, such as formalin, for preparation of a cell block to evaluate p16 immunohistochemistry or HPV in situ hybridization (OPHNSCC) or Epstein barr in situ hybridization (nasopharyngeal carcinoma).

The skin that overlies the mass is prepared with a prepackaged, sterile, alcohol preparation sponge that contains 70% isopropyl alcohol. For right-handed surgeons, the mass is grasped with the left hand and held in a fixed and stable position.

A 10-mL disposable syringe with an attached 21-gauge needle is placed just under the skin surface. Negative suction is applied to the syringe. The negative pressure is created and maintained by pulling the syringe plunger back. The mass is entered, and multiple passes are made without exiting the skin surface. Approximately 6 passes through the mass are recommended. If a cyst is encountered, it should be completely evacuated, with fluid sent for cytology. Recall that the cyst fluid may "dilute" the specimen and make cytologic interpretation impossible. Accordingly, aspirating the solid portions of the mass is ideal. The vacuum on the syringe is then released, and the skin is exited.

A small drop of aspirated fluid is placed on a glass slide, as shown in the first image below. A smear is made by laying another glass slide on top of the drop of fluid and pulling the slides apart to spread the fluid, as shown in the second image below. Wet smears are placed in 95% ethyl alcohol and treated with the Papanicolaou technique and stains. These stains offer excellent cellular detail and may indicate the cellular origin of a metastatic tumor. Specimens should be air dried and prepared for Wright-Giemsa stain when the differential diagnosis includes salivary, lymphoproliferative, and/or fatty tumors.

Photograph showing an aspirate being placed on a g Photograph showing an aspirate being placed on a glass slide. After the 20-mL disposable syringe with an attached 21-gauge needle is placed under the skin surface and the mass is aspirated, a small drop of aspirated fluid is placed on a glass slide.
Photograph showing the smear technique for plating Photograph showing the smear technique for plating a sample aspirate. After a small drop of fluid is placed on a glass slide, a second slide is used to smear the aspirate evenly over the surface of the slide. The slide is then prepared for cytologic evaluation.

The following common technical errors lead to inadequate specimens:

  • Aspirating a mass without a syringe holder

  • Aspirating a mass without moving the needle back and forth through the specimen (to dislodge the cells)

  • Aspiration of air after the biopsy is completed and the needle is withdrawn, allowing the small specimen to be lost in the syringe

Other nontechnical errors of specimen collection include the collection of necrotic and/or fibrotic specimens.

Some debate exists about what constitutes an adequate specimen for cytopathological diagnosis by FNA. When aspirates are placed on slides, clusters of cells form. Clusters contain approximately 10 cells, and at least several clusters of 8–10 cells are needed for interpretation. In a 1997 review of FNA of breast masses, Layfield and colleagues indicated that FNA smears with 6 or more cell clusters decrease the false-negative rate to 2.1% and decrease the percentage of inadequate specimens to 13.7%. [55] However, if slides that contain fewer than 6 clusters of breast tissue were excluded, 40% of true-negative and 4.5% of true-positive slides would be lost to analysis. The authors conclude that sampling adequacy should be based on the confidence of needle placement, cell preservation, and correlation with clinical findings.

Interpretation of cytopathology results requires an understanding of the nomenclature used for these test results and ancillary testing such as flow cytometry. For example, in thyroid lesions, the National Cancer Institute hosted a conference that resulted in terminology and criteria needed for diagnosis that is now widely employed by cytopathologists (The Bethesda System). [56]

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Pearls

When the diagnosis is uncertain, fine-needle aspiration (FNA) can almost always help.

The results of FNA may contribute to establishing the diagnosis but should not be accepted as absolute when clinical or other information contradicts the FNA findings.

The accuracy of FNA is increased by providing the cytopathologist accurate clinical information. It may be further enhanced by having the pathologist chairside during the procedure, allowing for immediate pathologic confirmation of the adequacy of the specimen. Further passes can be undertaken when acellular yields are encountered. If the specimen suggests a lymphoproliferative process, a specimen can be obtained for flow cytometry.

The overall yield of FNA is enhanced with image guidance. The most common approach is to use ultrasonography; however, CT guidance is commonly used.

Understanding the difference between an adequate specimen with indeterminate results and an inadequate specimen is of paramount importance

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Complications

Complications of FNA are rare. Hematoma and bruising are reduced with proper application of compression after the procedure.

FNA adjacent to vital structures or in deeply placed masses can be made more safe with the use of CT or US guidance.

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