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Thyroid nodule fine needle aspiration biopsy is generally carried out in the setting of a palpable nodule or ultrasound-detected thyroid nodule in order to confirm or exclude a malignant nodule. It is the most cost-effective initial method for guiding the clinical management of patients with thyroid nodules.
Palpable thyroid nodules are estimated to occur in 1% of males and 5% of females living in non-iodine deficient locations. Ultrasound evaluation of the thyroid reveals nodules in 16–67% of adults, women more commonly than men and the large majority are benign nodules. Not all palpable nodules correspond with a discrete abnormality when the area is examined with ultrasound and, by definition, these are not considered thyroid nodules. On the other hand, nodules detected on ultrasound may not be clinically palpable, but may have the same malignant potential as palpable nodules of the same size and thus should be dealt with similarly. Certain characteristics of nodules detected with ultrasound increase the likelihood of the nodule being malignant.
The incidence of thyroid cancer is increasing. So-called ‘differentiated’ (papillary and follicular) cancers comprise up to 90% of all thyroid cancers. The chance of any given nodule being malignant depends on:
Several characteristics of nodules on investigation influence the likelihood of thyroid malignancy:
An ultrasound-detected or clinically palpable nodule that is ‘hot’ (or shows increased uptake) on pertechnetate nuclear medicine thyroid scan is so unlikely to be a cancer that biopsy is not recommended . However, care must be taken to ensure that the ‘hot’ area on the nuclear medicine scan corresponds to the ultrasound detected or clinically palpable lesion. This is not always straightforward, especially when multiple nodules are present, as is commonly the case, particularly in adult females who have lived for many years in an area where the soil is deficient in iodine.
The appearance of the nodule on ultrasound.
A number of ultrasound features suggest an increased likelihood that a given thyroid nodule is malignant and they include:
Ultimately, the decision to perform FNA on any given nodule will be made based on a variety of clinical considerations including the results of other imaging as well as the sonographic appearance of lesion.
The most recent guidelines from the American Thyroid Association  recommend that patients with a clinically suspected thyroid nodule receive:
The serum TSH measurement is carried out for the following reasons:
Thyroid ultrasound is carried out in order to:
There are no absolute contraindications, as the needle used for this procedure is very small, but profound coagulopathy and inability of the patient to co-operate with the procedure (e.g. altered conscious state, dementia or communication difficulties of any kind) increase the risk of bleeding into the thyroid bed (see risks).
Thyroid FNA should be carried out as a targeted procedure on a lesion in the thyroid that has malignant potential, so lack of a focal abnormality is a relative contraindication to the procedure.
A known coagulation disorder (intrinsic or iatrogenic) can increase the risk of bleeding with this procedure. However, a recent systematic review by Polyzos  states that standard anticoagulation within an acceptable therapeutic range should not be a contraindication to FNA.
For patients taking antiplatelet or anticoagulant medication, provided it is considered medically safe to temporarily stop the medication, cessation is advisable before FNA. Radiology practice and hospital-specific policies exist regarding cessation of these medications.
The following parameters are recommended in order to minimise the risk of postprocedural haemorrhage in patients undergoing thyroid FNA:
This issue has been addressed in a recent systematic review. 
The major risks are bleeding and indeterminate biopsy result.
Blood extravasation related complications. This is more common in patients who have a lesion that is deep or when the lesion has a cystic component >50% of the whole lesion size. The review found extravasation occurred between 1.6 and 6.9% of all FNA procedures. The risk is a little higher with cystic compared with solid nodules. Just seven cases of life-threatening haemorrhage were reported in a series of over 17,000 FNA procedures.
The commonest manifestation of bleeding is local pain and tenderness, possibly mild dysphagia, and sometimes visible local swelling.
The risk of bleeding diminishes with:
Indeterminate result/inadequate specimen
This is unfortunately not uncommon, and complicates clinical management with regard to decisions about what to do next. Indeterminate results are less common when the FNA is performed by someone who does the procedure regularly and is experienced.The presence of a cytologist or cytology technologist can reduce the likelihood of an inadequate specimen by viewing it at the time of the procedure and informing the radiologist about whether or not another specimen is needed. This also has the potential to reduce bleeding complications by reducing the number of needle passes beyond what is required for a diagnosis.
Note that papillary cancers are diagnosed on the basis of features indicative of nuclear atypia in individual cells and thus can be diagnosed based on a good quality FNA specimen. Follicular cancers, on the other hand, are diagnosed based mainly on histological characteristics and thus specimens containing follicular cells may be cancer, adenoma or even a non-neoplastic colloid nodule within a goitre. Thus, when follicular cells are retrieved in an FNA, even when the amount of material is adequate, the result will be reported as indeterminate and either ultrasound follow up (to assess for growth), repeat FNA or removal of the nodule and/or hemithyroid will be needed depending on the level of clinical suspicion.
All of these occur more rarely than haemorrhage, but you should be aware of them in patients who have had FNA:
An open surgical biopsy is the alternative way to biopsy the thyroid
The results of FNA are traditionally divided into:
The addition of two more categories to this classification has recently been suggested 
Suspicious for malignancy (risk 50–75%).
Follicular lesion of undetermined significance (5–10% risk of malignancy).
It has also been suggested in this same guideline that the ‘indeterminate’ category be changed to: ‘neoplasm, either follicular or Hurtle cell (risk of malignancy 15–25%)’.
There is emerging evidence for the role of genetic testing of aspirated material for somatic mutations (e.g. BRAF) in reducing the rate of indeterminate FNA.
Between 15 and 30% of thyroid FNA results are inconclusive. Lesions that are more than 50% cystic on ultrasound or very small (<10mm) lesions are more likely to yield indeterminate results. Inconclusive results are also more likely with inexperienced operators.
Patients with indeterminate results or inadequate material should be considered for repeat FNA. The decision for repeat FNA should be influenced by the presence or absence of ultrasound signs suggesting malignancy as well as consultation with an endocrinologist and / or endocrine surgeon.
Suen KC. Fine-needle aspiration biopsy of the thyroid. Canadian Medical Association Journal, 2002. 167(5): p. 491–495:
Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer:
Tan, G.H. and H. Gharib, Thyroid incidentalomas: management approaches to nonpalpable nodules discovered incidentally on thyroid imaging. Ann Intern Med, 1997. 126(3): p. 226-31.
Liu, Y.I., et al., A Bayesian Network for Differentiating Benign From Malignant Thyroid Nodules Using Sonographic and Demographic Features. American Journal of Roentgenology, 2011. 196(5): p. W598-W605.
Cooper, D.S., et al., Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid, 2009. 19(11): p. 1167-214.
Polyzos, S.A. and A.D. Anastasilakis, Clinical complications following thyroid fine-needle biopsy: a systematic review. Clin Endocrinol (Oxf), 2009. 71(2): p. 157-65.
Polyzos, S.A., et al., Epidemiologic analysis of thyroid fine needle aspiration biopsies over a period of 18 years (1987-2004). Exp Clin Endocrinol Diabetes, 2008. 116(8): p. 496-500.
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