Molecular Markers in the Diagnosis of Thyroid Cancer in Indeterminate Thyroid Nodules

The Bethesda System for the Reporting of Thyroid Cytology recognises six diagnostic categories of thyroid nodule cytology with an incremental risk of malignancy. Although the Bethesda system created a much-needed handhold by standardising the cytological diagnosis and management of thyroid nodules worldwide, the system does not provide a clear answer to the heterogeneous group of nodules with indeterminate cytology. Improvement in the assessment of indeterminate fine-needle aspiration (FNA) results with molecular testing allows better risk stratification and reduces the need for diagnostic thyroid surgery. The molecular markers are classified as a "rule out" test, which has a high negative predictive value and helpful in cases with a low pre-test probability of cancer to rule out thyroid cancer. The "rule in" test has a high positive predictive value and helps in confirming malignancy in those with a high pre-test probability of cancer. This review summarises the commonly used molecular studies in thyroid FNAC aspirates and their current role in clinical practice.