The actual and future role of molecular tests in thyroid pathology

Thyroid nodules represent a common clinical challenge, with 20-30% of fine-needle aspiration biopsies yielding indeterminate cytology results that complicate management decisions. While fine-needle aspiration cytology (FNAC) remains the gold standard for initial evaluation, up to 30% of cases produce indeterminate results, often leading to unnecessary diagnostic surgeries. This comprehensive review examines the transformative role of molecular diagnostics in thyroid pathology, focusing on their clinical utility, prognostic implications, and future directions. Molecular testing platforms, including Afirma GSC, ThyroSeq v3, and ThyroidPrint, have transformed the management of indeterminate thyroid nodules through gene expression profiling, mutation analysis, and microRNA signatures. The third-generation tests exhibit high sensitivity (91-100%) and negative predictive values (90-100%), thereby enabling surgical avoidance rates of 50.3-68.6% for patients with indeterminate cytology. The platforms employ both "rule-out" strategies (high sensitivity/NPV) and "rule-in" approaches (high specificity/PPV) to guide clinical decision-making. The paradigm of classifying thyroid tumors based on BRAF-like and RAS-like molecular profiles is becoming increasingly entrenched in clinical and diagnostic practice, affording pathologists and clinicians the ability to render diagnoses that are both more precise and reproducible. Within this molecular framework, the identification of markers such as TERT promoter and TP53 mutations, along with gene fusions, provides not only refined prognostic information but also facilitates the selection of patients for targeted therapeutic regimens including BRAF/MEK inhibitors and RET inhibitors. Nevertheless, the implementation of these advances is not without its impediments. The field continues to grapple with platform heterogeneity, economic constraints, and geographic disparities affecting access to comprehensive molecular diagnostics-factors that necessitate ongoing efforts to standardize testing and expand global availability. The future of this field is marked by several key developments, including the expansion of next-generation sequencing, the advancement of liquid biopsy technologies, the integration of artificial intelligence, and the adoption of multi-omic approaches. International guidelines are increasingly recommending molecular testing for advanced thyroid cancers and indeterminate nodules. These guidelines emphasize the need for standardized protocols and equitable access to such testing. Molecular diagnostics should be embraced as complementary tools within multidisciplinary care to optimize patient outcomes while reducing unnecessary interventions in thyroid nodule management.