What are malignant thyroid nodules?

Updated: Aug 19, 2020
  • Author: Daniel J Kelley, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Thyroid carcinoma represents approximately 1% of all new cancers reported in the United States (about 12,000/y) and 92% of all endocrine gland cancers. Despite the low number of clinically evident cases, incidence of occult thyroid carcinoma has been reported in the range of 4.2-10% of all autopsy specimens. Variation in the incidence of autopsy cases depends on the study population, method of examination, and prior radiation exposure. Discrepancy between occult and reported cases of thyroid cancer suggests significant variations in screening and biologic behavior of the tumor. Additionally, the relatively high incidence of occult thyroid cancer at autopsy may imply a benign clinical course. Despite these facts, death due to uncontrolled local, regional, and distant disease can occur from thyroid cancer, and appropriate management is important in these cases.

The sex and age of the patient appear to play an important role in the clinical outcome of patients with malignant neoplasms of the thyroid gland. Although solitary thyroid nodules are found more frequently in women, incidence of carcinoma in solitary thyroid nodules is increased in men. Several studies have reported a bimodal age distribution of thyroid carcinoma in solitary thyroid nodules. Reported prevalence of thyroid carcinoma in an asymptomatic nodule is 3.4-29%. Data in medical literature are conflicting regarding increased prevalence of thyroid carcinoma in solitary nodules in the elderly population.

History of prior radiation exposure is an important risk factor for thyroid carcinoma. The risk of developing thyroid carcinoma increases following radiation exposure and is dose-dependent. Data collected from large populations intentionally or accidentally exposed to radioactive material have established a clear relationship between radiation exposure and thyroid cancer. Other risk factors include preexisting benign thyroid disease, irregular menstruation, bilateral oophorectomy, family history of thyroid malignancy, certain inherited syndromes, and residence in endemic goiter areas. Long-term alcohol and tobacco use do not appear to increase the risk of thyroid cancer.

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