ETA2023 Poster Presentations Translational 1 (9 abstracts)
1Institute of Endocrinology, Department of Molecular Endocrinology, Prague, Czech Republic; 22nd Faculty of Medicine, Charles University in Prague and Motol University Hospital, Department of Nuclear Medicine and Endocrinology, Prague, Czech Republic; 32nd Faculty of Medicine, Charles University in Prague and Motol University Hospital, Department of Etn, Prague, Czech Republic; 42nd Faculty of Medicine, Charles University in Prague and Motol University Hospital, Department of Pathology and Molecular Medicine, Prague, Czech Republic; 51st Faculty of Medicine, Charles University in Prague and Motol University Hospital, Department of Otorhinolaryngology and Head and Neck Surgery, Prague, Czech Republic; 62nd Faculty of Medicine, Charles University in Prague and Motol University Hospital, Department of Surgery, Prague, Czech Republic; 73rd Faculty of Medicine, University Hospital Kralovske Vinohrady, Department of Pathology, Prague, Czech Republic; 83rd Faculty of Medicine, University Hospital Kralovske Vinohrady, Department of Otorhinolaryngology, Prague, Czech Republic
Objectives: The substitution BRAF p.V600E is the most common genetic cause of the papillary thyroid carcinoma (PTC) and represents more than 95% genetic variants in BRAF gene. Other rare variants in the BRAF gene include other substitutions (e.g. p.K601E), small deletions or insertions close to codon 600. The aim of this study was to analyze a large cohort of thyroid nodules for rare genetic variants in the BRAF gene.
Methods: A total of 1282 fresh frozen thyroid tissues collected from 2003 to 2023 were screened for alterations of BRAF exon 15 by next generation sequencing. The cohort consisted of 837 PTC, 45 low-risk tumors, 36 oncocytic and follicular carcinomas (FTC), 7 poorly differentiated carcinoma, 17 anaplastic carcinomas and 323 benign tissues. The exon 15 of the BRAF gene was analyzed by next generation sequencing using the Nextera XT Sequencing Kit (Illumina) or Thyro-ID (4 bases). The VarSome software was used to interpret detected variants.
Results: Pathogenic variants in BRAF gene in 413 samples including the rare BRAF alterations in 14 samples - 11 PTC (1.3%), two benign nodules (0.6%) and one FTC (2.8%) - were detected. Eight various variants were detected. The most common were p.K601E, V600_K601delinsE and p.T599dup in four, three and two patients, respectively, followed by p.T599_V600insEAT, p.V600E+p.Q609E, p.A598_T599insI, p.V600_S605delinsEG and VKS600-2DFT in one case only. Except for p.K601E in one FTC and one benign nodule and p.T599dup in one benign nodule, other rare variants were found exclusively in PTC. The variants were evaluated as pathogenic or likely pathogenic using ACMG Classification. In one patient, pathogenic variant c.3140A>G p.(His1047Arg) in PIK3CA gene along with BRAF p.A598_T599insI variant was detected, in other patients with rare BRAF variants, no pathogenic variants in other main genes were detected.
Conclusions: The rare BRAF variants represented 3.4% of BRAF-positive thyroid nodules and their detection is only possible by sequencing. Except for p.K601E and p.T599dup, other rare variants were found exclusively in PTC. Supported by AZV NU21-01-00448 and MH CZ RVO 00023761.