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ESSENTIALS OF DIAGNOSIS
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ESSENTIALS OF DIAGNOSIS
Single or multiple thyroid nodules are commonly palpated by the patient or clinician or discovered incidentally on imaging studies.
Thyroid function tests recommended.
FNA cytology for thyroid nodules ≥ 1 cm or for smaller nodules when prior head-neck or chest-shoulder radiation.
Ultrasound guidance improves FNA diagnosis for palpable and nonpalpable nodules.
Clinical follow-up required.
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GENERAL CONSIDERATIONS
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Thyroid nodules are extremely common. Palpable nodules occur in 4–7% of all adults in the United States. They are much more common in women than men and become more prevalent with age. About 87% of palpable thyroid nodules (1 cm or larger) are benign adenomas, colloid nodules, or cysts, but some are primary thyroid malignancies or (less frequently) metastatic malignancy. On MRI, incidental small thyroid nodules are found in about 50% of adults. Thyroid nodules 1 cm or larger warrant follow-up and further testing for function and malignancy; an occasional smaller nodule requires follow-up if it has high-risk characteristics on ultrasound or if the patient is at high-risk for thyroid cancer due to prior head-neck radiation therapy during childhood. Thyroid nodules that are incidentally discovered with increased standard uptake value (SUV) on 18FDG-PET scanning have a 33% risk for being malignant and require FNA cytology.
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Most patients with a thyroid nodule are euthyroid, but there is a high incidence of hypo- or hyperthyroidism. Patients with multiple thyroid nodules have the same overall risk of thyroid cancer as patients with solitary nodules. The risk of a thyroid nodule being malignant is higher in men and among patients with a history of head-neck radiation, total body radiation for bone marrow transplantation, exposure to radioactive fallout as a child or teen, a family history of thyroid cancer or a thyroid cancer syndrome (eg, Cowden syndrome, multiple endocrine neoplasia type 2, familial polyposis, Carney syndrome), or a personal history of another malignancy. The risk of malignancy is also higher for large solitary nodules and if there is hoarseness or vocal fold paralysis, adherence to the trachea or strap muscles, cervical lymphadenopathy. The presence of autoimmune thyroiditis does not reduce the risk of malignancy; a nodule of 1 cm or larger in a gland with thyroiditis carries an 8% chance of malignancy.
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Table 26–6 illustrates how to evaluate thyroid nodules based on the index of suspicion for malignancy.
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