Molecular testing in thyroid cancer

Thyroid cancer is the most common endocrine malignancy. Thyroid cancer typically manifests as a thyroid nodule, although the majority of thyroid nodules are benign. Several strategies exist to diagnose cancer in a thyroid nodule, including ultrasound evaluation, fine needle aspiration (FNA) with cytology evaluation and/or molecular testing. Cancer-associated molecular alterations occurring in the majority of thyroid cancers have been uncovered, with the most common being mitogen-activated protein kinase (MAPK) pathway gene mutations or fusions. Several molecular panels are available for the evaluation of thyroid FNA samples and may help to refine the probability of cancer, predict histologic cancer type, estimate risk of cancer recurrence, and identify potential therapeutic targets. This chapter reviews the molecular alterations characteristic of thyroid cancer and available molecular technologies along with their clinical utility and limitations.