TERT Promoter Mutations in Papillary Thyroid Microcarcinomas

Background: Small papillary thyroid carcinomas have contributed to the worldwide increased incidence of differentiated thyroid cancer observed over the past decades. However, the mortality rate has not changed over the same period of time, raising questions about the possibility that thyroid cancer patients, especially those with small tumors, are overdiagnosed and overtreated. Molecular prognostic marker able to discriminate aggressive thyroid cancers from those with an indolent course would be of great relevance to tailor the therapeutic approach and reduce overtreatment. Mutations in the TERT promoter were recently reported to correlate strongly with aggressiveness in advanced forms of thyroid cancer, holding promise for a possible clinical application. The occurrence and potential clinical relevance of TERT mutations in papillary thyroid microcarcinomas (mPTCs) is currently unknown. This study aimed to analyze the occurrence of two TERT promoter mutations (-124C>T and -146C>T) and their potential association with unfavorable clinical features in a large cohort of mPTCs. Methods: A total of 431 mPTCs cases were collected from six Italian institutions, and TERT promoter mutational status was assessed by a next-generation sequencing approach. Results: TERT promoter mutations were found in 4.7% of the analyzed mPTCs, showing that even microcarcinomas carry mutations in this gene. Correlation analysis showed that TERT promoter mutations are not associated with aggressive features or clinical outcome in the cohort analyzed. Conclusions: TERT mutations are present but uncommon in mPTCs. Apparently, in mPTCs, the occurrence of TERT mutations is not correlated with unfavorable clinical features.