Diagnostic and prognostic TERT promoter mutations in thyroid fine-needle aspiration biopsy

Two promoter mutations, chr5:1 295 228C>T and chr5:1 295 250C>T, in the gene for telomerase reverse transcriptase (TERT) have been recently identified in thyroid cancers and shown to be important in thyroid tumor pathogenesis. The diagnostic and prognostic potentials of testing for these mutations on thyroid fine-needle aspiration biopsy (FNAB) have not been investigated. Herein, we examined the two TERT promoter mutations along with the BRAF V600E mutation by direct DNA sequencing on 308 FNAB specimens preoperatively obtained from thyroid nodules with postoperatively confirmed pathological diagnoses. We found TERT promoter mutations in 0.0% (0/179) of benign thyroid nodules and 7.0% (9/129) of thyroid nodules of differentiated thyroid cancer, representing a 100% diagnostic specificity and 7.0% sensitivity, with the latter rising to 38.0% (49/129) when combined with BRAF V600E testing. Several TERT-promoter-mutation-positive thyroid nodules were cytologically indeterminate on FNAB. Approximately 80% of the TERT promoter mutation-positive thyroid nodules were thyroid cancers with aggressive clinicopathological behaviors, such as extrathyroidal invasion, lymph node metastases, distant metastases, disease recurrence or patient death. Thus, a positive TERT promoter mutation test not only definitively diagnoses a thyroid nodule as cancerous but also preoperatively identifies a cancer with aggressive potential. This is the first study, to our knowledge, of TERT promoter mutations on thyroid FNAB, demonstrating the value of this novel molecular testing in the diagnosis of thyroid nodules and preoperative risk stratification of thyroid cancer. Thus, testing of TERT promoter mutations on FNAB will enhance and improve the current molecular-based approaches to the management of thyroid nodules and thyroid cancer.