ECE2022 Eposter Presentations Thyroid (219 abstracts)
Objectives: Papillary thyroid carcinoma (PTC) is the most frequent malignant endocrine disease and the most common genetic cause of the PTC is the substitution c.1799T>A (p.V600E) in the BRAF gene (35-70% of PTC) that represents more than 95% of BRAF mutations. Other rare mutations in the BRAF gene include other substitutions (e.g. p.K601E), small deletions or insertions close to codon 600. The aim was to analyze a large cohort of thyroid nodules for rare genetic variants in the BRAF gene.
Methods: A total of 1106 fresh frozen thyroid tissues collected from 2003 to 2021 were screened for exon 15 BRAF alterations. The cohort consisted of 851 papillary thyroid carcinomas (PTC), 33 borderline tumors, 28 oncocytic and follicular carcinomas (FTC), 6 poorly differentiated carcinoma (PDTC), 15 anaplastic carcinomas (ATC), 15 follicular adenomas (FTA) and 122 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: The most common BRAF mutation p. V600E was detected in a total of 430 thyroid tissues - in 425 PTC, two borderline tumors (NIFTP and WDT-UMP), one PDTC and two ATC. In total, BRAF p.V600E was detected in 51.3% of PTC. The rare somatic BRAF alterations were detected in 11 from 851 patients of PTC (1.29%), in one benign thyroid tissue and one FTC. We detected eight various variants - the most common was p.K601E and V600_K601delinsE in four and three patients, respectively, followed by p.V600E+p.Q609E, p.V600_S605delinsEG, VKS600-2DFT, p.T599_V600insEAT, p.A598_T599insI and p.T599dup in one case only.
Conclusions: The rare BRAF variants represented 2.9% of BRAF-positive thyroid nodules. Except for p.K601E, other rare variants were found exclusively in PTC. However, BRAF fusion genes, that seem to be other genetic causes of PTC, were not analyzed in this study. Supported by AZV NU21-01-00448 and MH CR RVO 00023761.
21 May 2022 - 24 May 2022