A thyroid nodule is a discrete lesion distinct from the surrounding thyroid parenchyma. Enlargement of other nearby anatomic structures, such as the parathyroid glands or regional lymph nodes, as well as branchial cleft and thyroglossal duct cysts, may sometimes be confused with thyroid nodules.
Thyroid nodules are a common clinical problem.[1] They can be found in 50% to 60% of healthy people.[2] Most thyroid nodules are asymptomatic and are detected by palpation or incidentally detected during an imaging procedure.[3] In an international retrospective analysis of patients who underwent thyroid-directed surgery, radiologic procedures performed for other indications detected thyroid nodules in 20% of cases.[4] Incidental detection of thyroid nodules is thought to be behind an increased reported incidence of thyroid cancers globally.[5]
Thyroid nodules are more common in female patients.[1][4] The prevalence of thyroid nodular disease increases with advancing age.[6] Despite this increase in nodularity, thyroid nodules in older adults have a lower risk of malignancy; however, when thyroid cancer is identified, it is more likely to be of high-risk histology.[6] [7] Autopsy studies detect nodules in over half of the general population by the fifth or sixth decades of life.[8]
