Molecular Profiling of Papillary Thyroid Carcinoma in Korea with a High Prevalence ofBRAFV600EMutation

Background: The BRAFV600E mutation in papillary thyroid carcinoma (PTC) is particularly prevalent in Korea, and a considerable number of wild-type BRAF PTCs harbor RAS mutations. In addition, subsets of other genetic alterations clearly exist, but their prevalence in the Korean population has not been well studied. Recent increased insight into noninvasive encapsulated follicular variant PTC has prompted endocrine pathologists to reclassify this entity as “noninvasive follicular thyroid neoplasm with papillary-like nuclear features” (NIFTP). This study analyzed the genetic alterations among the histologic variants of PTC, including NIFTP. Methods: Mutations of the BRAF and RAS genes and rearrangement of the RET/PTC1, NTRK1, and ALK genes using 769 preoperative fine-needle aspiration specimens and resected PTCs were analyzed. Results: Molecular alterations were found in 687 (89.3%) of 769 PTCs. BRAFV600E mutation (80.8%) was the most frequent alteration, followed by RAS mutation and RET/PTC1, NTRK1, and ALK rearrangements (5.6%, 2.1%, 0.4%, and 0%, respectively). The low prevalence of NTRK1 fusions and the absence of an ALK fusion detected in Korea may also be attributed to the higher prevalence of the BRAFV600E mutation. There were significant differences in the frequency of the genetic alterations among the histologic variants of PTC. The prevalence of NIFTP in PTC was 2.7%, and among the NIFTPs, 28.6% and 57.1% harbored BRAF and RAS mutations, respectively. Clinicopathologic factors and mutational profiles between NIFTP and encapsulated follicular variant PTC with capsular invasion group were not significantly different. Conclusions: Genetic alterations in PTC vary among its different histologic variants and seem to be different in each ethnic group.