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Thyroid nodule sonography: assessment for risk of malignancy

Jill E Langer and Susan J Mandel

Fine-needle aspiration (FNA) is the most reliable diagnostic tool for diagnosing thyroid cancer and should be performed on nodules considered suspicious. Traditionally, thyroid nodules were discovered by physical examination of the neck and underwent palpation-guided FNA in the physician’s office when malignancy was of concern. In recent years, the use of high-resolution neck sonography to examine the thyroid has resulted in the detection of many nonpalpable nodules. Although the majority of these nodules are benign, their discovery results in the need to determine if FNA should be performed on one or more of these nodules. The goal is to be able to diagnose all biologically significant cancers, while exposing the fewest number of patients with benign disease to unnecessary diagnostic testing. Sonography of the neck has emerged as the primary imaging means to evaluate the malignant potential of thyroid nodules. Although no single sonographic feature can be used to detect all cancerous nodules, some sonographic features such as calcifications, marked hypoechogenicity, infiltrative margins and ‘taller-than-wide’ shape are relatively specific for thyroid cancer. By using sonographic criteria to stratify risk of malignancy, invasive and costly evaluations can be avoided in many patients without missing the minority of patients who have a thyroid malignancy.