chapter  1
Fine Needle Aspiration of the Head and Neck
Pages 94

Although clinically palpable thyroid nodules are only present in 4% to 7% of the adult population in the United States, the increasing use of diagnostic imaging has greatly increased the frequency of incidentally discovered thyroid nodules with a prevalence as high as 50% in many studies (1,2). These incidental thyroid nodules are usually detected with head and neck ultrasound (US) studies for carotid or parathyroid disease, and on computed tomography (CT), magnet resonance imaging (MRI), or positron emission tomography (PET) scans for the work-up of metastatic disease unrelated to the thyroid. However, the prevalence of cancer appears to be similar in palpable and nonpalpable thyroid nodules, ranging from 5% to 8 %, with microinvasive papillary carcinomas being increasingly diagnosed at earlier stages because of widespread use of high-resolution US (1).