Low frequency of TERT promoter mutations in a series of well-differentiated follicular-patterned thyroid neoplasms

The diagnostic and clinical approaches to follicular-patterned thyroid neoplasms often create dilemmas for pathologist and clinicians. The molecular analysis of these tumors could be a useful tool to overcome diagnostic limitations. The most frequent molecular alterations are point mutations of RAS family genes. Nevertheless, other molecular markers should be taken into account for their prognostic role, as BRAF mutations and the recently described telomerase reverse transcriptase (TERT) promoter mutation. We investigated the prevalence and the possible role of TERT promoter, BRAF, and RAS mutations in a series of low-risk well-differentiated follicular-patterned thyroid neoplasms. We evaluated 60 follicular adenomas (FA), 29 minimally invasive follicular carcinomas (MIFTC), 82 papillary carcinomas, follicular variant (FVPTC), and 16 noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFT-P) for the molecular status of BRAF, H-, N-, K-RAS, and TERT and correlated it with clinic-pathological parameters of tumors. Fifty-seven (30.5%) follicular neoplasms were mutated. In particular, we found 44 RAS mutated neoplasms (23.5%), specifically three FAs, 29 FVPTCs, five NIFT-Ps, and seven FTCs. BRAF mutations were found in ten FVPTCs. Finally, TERT promoter mutations were observed in three FVPTCs and three FTCs; three of them harbored also N-RAS mutations. We confirmed the absence of TERT promoter mutations in benign follicular neoplasms and found a low frequency of TERT promoter mutations in our selected cohort of low-risk follicular-patterned malignancies, speculating their role in the progression and de-differentiation of thyroid cancer.