Role of Ultrasonography in the Diagnosis and Management of Thyroid Cancer

Abstract

To review the role of ultrasonography in the detection and management of thyroid cancer. Viewpoints are presented on the appropriate applications and the advantages of ultrasonography, based on an extensive personal experience with more than 1,500 ultrasound examinations for assessment of thyroid nodules and for follow-up surveillance of patients with thyroid cancer. Ultrasonography is ideal for thyroid imaging because of the high echogenicity of thyroid tissue, the superficial site of the thyroid that allows the use of high-frequency transducers yielding high resolution, and the low expense compared with other techniques. In patients with a thyroid nodule, ultrasonography can assist in distinguishing benign from malignant disease. Ultrasound studies will characterize the presence of cystic versus solid elements, the degree of echogenicity of solid elements, the existence of calcifications, and the regularity and definition of the nodule borders. Although individual sonographic features of thyroid nodules are not specific for benign or malignant lesions, a constellation of typical features has more diagnostic value. Hypoechogenicity, poorly defined irregular margins, and microcalcifications are characteristics that should increase the index of suspicion for a malignant nodule. Cytologic examination of fine-needle aspirates is the optimal diagnostic test, and ultrasonographic guidance for performance of the aspiration biopsy is often helpful and sometimes critical. Ultrasonography is also useful for detection of cervical lymph node metastatic lesions. Lymph nodes involved with metastatic thyroid cancer tend to become rounded and bulging, and they lose their hilar echoes as their structure becomes disrupted. Because of its high resolution and relatively reasonable cost, ultrasonography is valuable in the diagnosis and management of thyroid cancer.