Thyroid Nodule

Background

• A thyroid nodule is a discrete lesion in the thyroid gland that is radiologically distinct from surrounding normal thyroid tissue.
• Thyroid nodules are detected in about 60% of adults. They are 4 times more common in female patients than in male patients and occur more frequently with increasing age.
• Most thyroid nodules are asymptomatic. Palpable nodules often are discovered on physical exams, and nonpalpable nodules frequently are detected incidentally on imaging studies performed for unrelated reasons.
• Symptomatic patients may report symptoms related to hyperthyroidism or hypothyroidism, compressive symptoms, or cosmetic concerns.
• Thyroid nodules may be caused by both benign (about 90%) and malignant (about 10%) lesions. Risk factors for malignancy include family history of thyroid cancer and history of radiation therapy.
• While thyroid nodules may be associated with thyroid dysfunction or local mass effects, the primary clinical concern is to identify and treat lesions that are malignant or at high risk for malignancy.

Evaluation

• A thyroid nodule can be detected by neck palpation during physical exam or incidentally diagnosed during imaging studies performed for an unrelated condition.
  • Once a thyroid nodule is identified, further evaluation includes a combination of clinical and ultrasound examination to determine clinical relevance (risk for malignancy, compressive symptoms, and thyroid dysfunction), and the need for additional diagnostic testing.
  • The evaluation of thyroid nodules is generally the same in children and adults. Avoid the use of radioactive agents in pregnant adults for diagnostic purposes (Strong recommendation).
• Begin the evaluation with a history and physical exam focused on identifying risk factors for malignancy, including:
  • a history of radiation therapy
  • a family history of thyroid cancer or multiple endocrine neoplasia type 2
  • rapid growth of nodule
  • hoarseness, dysphagia, or dyspnea
  • the presence of a firm, fixed nodule
• For all patients with a thyroid nodule, including those discovered as incidentaloma:
  • Perform an ultrasound of thyroid gland and neck (Strong recommendation).
  • Check thyroid-stimulating hormone (TSH) (Strong recommendation).
  • If TSH is decreased, measure thyroid hormone, perform radionuclide scan (Strong recommendation), and consider checking anti-TSH receptor antibody (TRAb) levels (Weak recommendation).
    • Hyperfunctioning ("hot") nodules on radionuclide scan have low malignancy risk (patients with low TSH and hot nodule should be evaluated and treated for hyperthyroidism).
    • Hypofunctioning ("cold") nodules on radionuclide scan require further evaluation for potential malignancy.
• For patients who are at increased risk for malignancy based on clinical and ultrasound findings, perform ultrasound-guided fine needle aspiration (FNA) biopsy for cytologic classification and determination of malignancy risk.
  • Consider ultrasound surveillance instead of FNA biopsy for (Weak recommendation):
    • most nodules ≥ 5 mm but < 1 cm, except with high-risk features
    • all nodules < 5 mm, regardless of ultrasound features
  • FNA biopsy is not indicated for purely cystic nodules (Strong recommendation).
• Molecular testing may further stratify the risk of malignancy in thyroid nodules with indeterminate cytology and, in so doing, is reported to reduce diagnostic surgeries. It is not routinely recommended for nodules with established benign or malignant cytology.
• Consider measuring serum calcitonin which may be increased in medullary thyroid carcinoma (Weak recommendation).

Management

• Management of thyroid nodules is guided by combination of:
  • clinical findings
  • ultrasound evaluation
  • cytopathologic evaluation by FNA biopsy (performed if appropriate)
• For thyroid nodules that do not meet the criteria for FNA biopsy, consider periodic monitoring based on ultrasound features and nodule size (Weak recommendation).
• Usual treatment based on Bethesda cytopathologic classification after FNA biopsy:

Table 1. Overview of Usual Management of Thyroid Nodules Based on Bethesda Category

• Pregnant adults and children are generally managed similarly to nonpregnant adults, except radioactive agents for any purpose should be avoided in pregnant adults (Strong recommendation).