Ultrasonographic, cytologic and genetic diagnosis of thyroid cancers

Kang, Ho Cheol

Abstract

Thyroid nodules are very common in adults, but only small fraction of them are malignant. The primary aim in investigating a thyroid nodule is to exclude the possibility of malignancy, which occurs in about 5% of nodules. Thyroid ultrasonography (US) provides not only anatomic details of the nodule, but also features of nodules that increase the likelihood of malignancy. Hypoechogenicity, ill-defined margin, microcalcifications, taller-than-wide shape, and associated pathologic cervical lymphadenopathies are important US features, suggesting thyroid cancer. These findings are helpful in risk stratification of the nodules and in deciding which nodule should be sampled in multinodular goiter. Fine-needle aspiration cytology (FNA) is the most accurate diagnostic test for most thyroid nodules, but the challenge remains in indeterminate cytologic category and inadequate samples. US-guided FNA can improve the diagnostic yield by reducing non-diagnostic specimens, and especially useful in thyroid nodules that are impalpable, posteriorly located, densely-calcified, or mixed solid-cystic. There has been significant progress in biomarkers that could improve the accuracy of FNA and predict disease aggressiveness. Physicians caring for patients with thyroid nodules need to develop a rational, cost-effective approach to ordering and interpreting imaging and diagnostic tests in the evaluation of the thyroid nodule.