The sonographic appearance of benign and malignant thyroid diseases and their histopathology correlate: demystifying the thyroid nodule.

The thyroid gland is one of the largest endocrine glands in the human body. It functions as a regulator of metabolism. Diseases involving the thyroid range from benign to malignant and can be associated with major morbidity and mortality. Ultrasound (US) imaging of the thyroid gland is prompted because of a palpable mass on clinical examination; abnormality of thyroid function tests; incidental finding on other imaging modalities, that is, nuclear scintigraphy or computed tomography scan; screening for patients with risk factors for malignancy, such as multiple endocrine neoplasia type II; or prior neck radiation treatment.Ultrasound is an excellent, noninvasive, and cost-effective diagnostic tool in the detection and characterization of thyroid disease. Most thyroid diseases have pathognomonic features on US, which are of diagnostic importance and lead to appropriate clinical management. Ultrasound plays an important role in differentiating benign from malignant thyroid disease, thereby triaging patients for US-guided fine-needle aspiration. Ultimately, thyroid US, in conjunction with thyroid function tests, can aid in characterizing various thyroid diseases.The main objective of this pictorial essay is to illustrate the sonographic appearance of various benign and malignant diseases of the thyroid with their histopathology correlations. Management of thyroid nodules using US-guided fine-needle aspiration is also briefly discussed.