%0 Journal Article
%T A comparison of the histopathologic features of thyroid carcinomas with NTRK fusions to those with other malignant fusions.
%A Tondi Resta I
%A Rind A
%A Montone KT
%A Livolsi VA
%A Baloch ZW
%J Hum Pathol
%V 149
%N 0
%D 2024 Jul 8
%M 38857659
%F 3.526
%R 10.1016/j.humpath.2024.06.004
%X <B>BACKGROUND: </B>Chromosomal rearrangements involving one of the NTRK genes result in oncogenic driver mutations in thyroid carcinoma (TC) and serve as a target for therapy. We compared the clinicopathologic features of thyroid carcinomas with NTRK fusions vs. thyroid neoplasms with other malignancy associated gene fusions within our institution.<BR><B>METHODS: </B>Our pathology archives were searched from 2013 to 2023 for thyroid neoplasms with gene fusions, excluding THADA fusions and medullary thyroid carcinomas.<BR><B>RESULTS: </B>55 thyroid lesions were identified: 22 with NTRK fusions (NTRK cohort) and 33 with other fusions (non-NTRK cohort). On fine needle aspiration (FNA), 54% of the NTRK cohort were classified as Category V as per Bethesda System for Reporting Thyroid Cytology (TBSRTC) and 51.5% of non-NTRK cohort as TBSRTC Category III. In the NTRK cohort, the most common reported fusion was ETV6::NTRK3 and the most common reported fusion in the non-NTRK cohort was PAX8::PPAR-gamma. On histologic examination both cohorts were most commonly diagnosed as PTC follicular variant. Invasive features were more common in the NTRK cohort in comparison to the non-NTRK cohort. Locoregional recurrence occurred in 2/22 NTRK cases and 2/33 non-NTRK cases, with average time from surgery to recurrence being 5.5 months and 21 months, respectively. The majority of patients in both groups are alive with no evidence of disease.<BR><B>CONCLUSIONS: </B>Thyroid neoplasms with a malignancy associated gene fusion are likely to be diagnosed as subtype/variant of PTC. Patients whose thyroid lesions harbor NTRK fusions present with a PTC-FV that on presentation has more aggressive clinicopathologic findings and are likely to have earlier disease recurrence.