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Occasionally, there may be nodules <1 cm that require further evaluation because of clinical symptoms or associated lymphadenopathy . In very rare cases, some nodules <1 cm lack these sonographic and clinical warning signs yet may nonetheless cause future morbidity and mortality. In general, the guiding clinical strategy acknowledges that most thyroid nodules are low risk, and many thyroid cancers pose minimal risk to human health and can be effectively treated.
Complete history and physical examination
With the discovery of a thyroid nodule, a full history and physical examination focusing on the thyroid gland and adjacent cervical lymph nodes should be performed.
Relevant historical factors predicting malignancy include:
What is the appropriate laboratory and imaging evaluation for patients with clinically or incidentally discovered thyroid nodules?
Nonpalpable nodules detected on US or other anatomic imaging studies are termed incidentally discovered nodules or ‘‘incidentalomas.’’ Non-palpable nodules have the same risk of malignancy, as do sonographically confirmed palpable nodules of the same size.
Serum thyrotropin measurement
Serum thyrotropin should be measured during the initial evaluation of a patient with a thyroid nodule. If the serum TSH is subnormal, a radionuclide preferably 123I thyroid scan should be performed. If the serum TSH is normal or elevated, a radionuclide scan should not be performed as the initial imaging evaluation.
Serum thyroglobulin measurement
Routine measurement of serum thyroglobulin for initial evaluation of thyroid nodules is not recommended.
Focal fluorodeoxyglucose positron emission tomography uptake within a sonographically confirmed thyroid nodule conveys an increased risk of thyroid cancer, and FNA is recommended for those nodules >1 cm. Diffuse 18FDG-PET uptake, in conjunction with sonographic and clinical evidence of chronic lymphocytic thyroiditis, does not require further imaging or FNA.
18FDG-PET is increasingly performed during the evaluation of patients with both malignant and nonmalignant illness. While 18FDG-PET imaging is not recommended for the evaluation of patients with newly detected thyroid nodules or thyroidal illness, the incidental detection of abnormal thyroid uptake may nonetheless be encountered. Importantly, incidental 18FDG-PET uptake in the thyroid gland can be either focal or diffuse. Focal 18FDG-PET uptake in the thyroid is incidentally detected in 1%–2% of patients, while an additional 2% of patients demonstrate diffuse thyroid uptake.
Thyroid sonography
Thyroid sonography with survey of the cervical lymph nodes should be performed in all patients with known or suspected thyroid nodules.
Thyroid US can answer the following questions:
Is there truly a nodule that corresponds to an identified abnormality?
How large is the nodule?
What is the nodule’s pattern of US imaging characteristics?
Is a suspicious cervical lymphadenopathy present?
Is the nodule more than 50% cystic?
Is the nodule located posteriorly in the thyroid gland?
These last two features might decrease the accuracy of FNA biopsy performed with palpation.
US for FNA decision-making
FNA is the procedure of choice in the evaluation of thyroid nodules, when clinically indicated.
FNA is the most accurate and cost-effective method for evaluating thyroid nodules.
Thyroid nodule diagnostic FNA
Thyroid US has been widely used to stratify the risk of malignancy in thyroid nodules, and aid decision-making about whether FNA is indicated.
Thyroid nodule diagnostic FNA is recommended for:
Nodules >1 cm in greatest dimension with high suspicion sonographic pattern.
Nodules >1 cm in greatest dimension with intermediate suspicion sonographic pattern.
Nodules >1.5 cm in greatest dimension with low suspicion sonographic pattern.
Indications for FNA biopsy according to US findings.
Suspicious US findings are a markedly hypoechoic nodule, intranodular microcalcifications, taller-than-wide shape, and spiculated or lobulated margins
What is the role of FNA, cytology interpretation, and molecular testing in patients with thyroid nodules?
Thyroid nodule FNA cytology should be reported using diagnostic groups outlined in the Bethesda System for Reporting Thyroid Cytopathology.
For a nodule with an initial nondiagnostic cytology result, FNA should be repeated with US guidance and, if available, on-site cytologic evaluation. If the nodule is benign on cytology, further immediate diagnostic studies or treatment are not required. If a cytology result is diagnostic for primary thyroid malignancy, surgery is generally recommended. The cytological report suggests the clinical action.
In Summary
Thyroid nodules that do not meet sonographic criteria for FNA should be monitored with periodic ultrasonography. The frequency of evaluation (ranging from 6 to 24 months) depends upon the sonographic features of the nodules.