ASPECTOS CLÍNICO-PATOLÓGICOS E PAINEL MULTIGÊNICO NO CARCINOMA DE TIREOIDE DERIVADO DE CÉLULAS FOLICULARES

Abstract

Introduction: Follicular cell-derived thyroid carcinoma (FCDTC) constitutes the majority of thyroid neoplasms, accounting for almost 90% of cases. The tumor molecular profile analysis, through the technique of next generation sequencing (NGS), has been essential for the tracking of actionable mutations in cancer and, consequently, in the identification of cases that may evolve to a more aggressive behavior of the disease. The clinical management of FCDTC has evolved due to a better understanding of the impacts of genetic alterations reported on the main gene drivers involved in the hyperactivation of the MAPK and PI3K-AKT pathways. However, the clinicopathological correlation of these genetic alterations is still poorly understood, especially in patients from Latin America. Objectives: To correlate clinicopathological aspects of FCDTC in adult patients with mutations through a customized multigenic panel. Material and Methods: Retrospective, cross-sectional, unicentric study, involving 100 adult patients diagnosed with FCDTC, between 2010 and 2019, at Hospital Aristides Maltez in Salvador, Bahia. The anatomopathological data were reviewed by a pathologist. Paraffinized tumor DNA was extracted with the ReliaPrep™ FFPE gDNA Miniprep System (Promega, USA). Genotyping of target genomic regions (KRAS, NRAS, BRAF, EGFR and PIK3CA) was performed using the customized Ampliseq panel and sequencing performed on the iSeq™ 100 platform (Illumina®, USA). Bioinformatics analyzes were performed on the cloud-based Varstation™ platform. Results: After performing the NGS technique, 54/100 (54%) presented satisfactory results, and 46/100 (46%) samples presented inconclusive results. Through our customized mutational panel, 31/54 (57%) of the samples had mutations in the analyzed genes, 83% of classic papillary subtype (CPTC), mean age of 34 years, 83% female, and mean tumor size of 2.21 cm. 23/54 (42.6%) did not present any mutation (wild). Mutations in the BRAF gene were the most frequent (≥58% of the mutations found), most of them present in CPTC. 10/54 (18%) samples had the BRAFV600E mutation, and surprisingly, we found 7 BRAFNO-V600E mutations not yet described in FCDTC (G464E, G464R, G466E, S467L, G469E, G596D and the T599Ifs*10 deletion) and the BRAFA598V mutation previously reported. BRAFG464E and BRAFG596D were detected in two cribform morular CT cases, BRAFG466E, BRAFG469E, BRAFG464R and BRAFA598V were present in CPTC, the BRAFT599Ifs*10 deletion observed in a solid variant of CPT, and BRAFS467L was present in one case of an infiltrative follicular variant from CPT and CPTC; all samples with absence of extrathyroidal extension (ETE). Mutations in the EGFR gene were found in 16/54 (29%) of the tumor samples, all of the CPTC subtype, and in the RAS genes (KRAS and NRAS), 8/54 (14%) mutations were found. No mutations were found in the PIK3CA gene. Interestingly, 12 samples had multiple mutations: 3 (BRAFV600/EGFR), 3 (BRAFNO-V600/EGFR), 2 (BRAFV600/BRAFNO-V600), 3 (BRAF/RAS), with 1 CPTC sample with 4cm and ETE present presented three mutations simultaneously in the KRASD119N, NRASQ61* and EGFRH850Rfs*26 genes. Conclusion: In this study, no significant association was found between FCDTC and BRAFV600E, KRAS, NRAS and EGFR mutations. However, the BRAFNO-V600E variants were significantly evident and associated with a lower risk of ETE. The findings of this study bring the relevance of carrying out a multigene panel by NGS in cases of FCDTC, with the purpose of expanding knowledge about the frequency and impacts of genetic alterations associated with this pathology.