What is the role for molecular testing of thyroid nodules?
About 15% to 30% of thyroid nodules are cytologically indeterminate on FNA (Bethesda III and IV), and the majority (60%–85%) of these nodules are benign. The goal of molecular diagnostic testing of thyroid nodules is to further stratify the risk of malignancy in those with indeterminate cytology to decrease the number of patients who undergo unnecessary surgery for benign disease. There are multiple commercially available tests that analyze for the genetic mutations/alterations and/or gene expression profiles known to occur in thyroid cancer. Although not perfect, some of these tests are now in their second (Afirma GSC) and third (Thyroseq v3.0) generation, and are reported to have excellent negative-predictive (95%) and reasonable positive-predictive (50%-70%) values. When appropriately utilized, these tests can safely and cost-effectively avoid unnecessary surgery in up to 20% of patients with indeterminate thyroid nodules.