Management of a Thyroid Nodule
The prevalence of thyroid nodules varies with the level of iodine sufficiency. Because iodine deficiency is relatively rare in the United States, only about 5% of US women will have a palpable thyroid nodule. In contrast, as many as 67% of women will have a detectable nodule when high resolution ultrasound is randomly used to examine the thyroid gland.
The clinical concern with detecting a thyroid nodule is the possibility of thyroid cancer, which may occur in up to 15% of cases. Even though most thyroid cancers are well differentiated, slow growing, and have an overall good prognosis, it is incumbent on the clinician to rule out a thyroid cancer when a palpable nodule is present.
Nodules greater than 1 cm in size, whether detected by palpation or incidentally found by imaging, merit a diagnostic evaluation. Regardless of how detected, the risk of cancer is the same. It is also appropriate to investigate nodules smaller than 1cm in patients when such nodules are associated with suspicious symptoms, lymphadenopathy, or clinical risk factors for cancer.
Risk factors for thyroid cancer include:
- Childhood head and neck irradiation
- Whole body irradiation for bone marrow transplant
- First-degree relative with thyroid cancer
Clinical findings concerning for cancer include:
- Rapid growth of a nodule
- Vocal cord paralysis
- Cervical lymphadenopathy
- Fixation to surrounding tissues
After initial history and physical exam, a TSH (thyroid stimulating hormone) and thyroid ultrasound should be obtained.
If the TSH level is low, a radionuclide thyroid scan should also be obtained to help determine whether the nodule is producing excess thyroid hormone, which in turn suppresses serum TSH (a “hot nodule”). Hyperfunctioning nodules are unlikely to be malignant, so fine needle aspiration for cytology is unnecessary. The ultrasound serves to confirm that the nodules of hyperfunctioning are concordant with the nodules demonstrated anatomically. Referral to an Endocrinologist for further management of the hyperthyroid state may be appropriate.
When the TSH is normal or elevated, ultrasound of the thyroid is used to confirm the presence of the nodule, determine its location, character, and assess for the presence of any suspicious cervical lymph nodes. FNA (fine needle aspiration) with ultrasound guidance is the procedure of choice for confirming the diagnosis based on ultrasound patterns of suspicion.
Presence of multiple nodules, such as might be found in a woman with a multinodular goiter, does not rule out malignancy. Sampling each nodule with an FNA is not practical, but ultrasound features of the nodules such as size, hypoechogenicity, micro calcifications and hypervascularity can be used to help predict the likelihood for malignancy and target nodules for biopsy.
Haugen BR, Alexander EK, Bible KC, et al., 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid. 2016 Jan;26(1):1-133. doi: 10.1089/thy.2015.0020.
Initial Approval January 2010. Revised September 2016. Reaffirmed January 2018. Reaffirmed July 2019
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