Thyroid cancer in children and adolescents is a rare disease but with an increasing incidence. As in adults, the most prevalent type is papillary thyroid carcinoma (PTC). Our aim was to describe the clinical and genetic comparison between pediatric and adult PTC. We analyzed the cohorts of 73 pediatric PTC (5-18 years, female to male ratio 2.3:1, 10 patients <10 years) and 460 adult PTC patients. DNA and RNA were extracted from cancer tissue samples. DNA was used for sequencing of TERT promotor C228T and C250T mutations with CEQ8000 and BRAF and RAS mutations by Nextera XT kit with MiSeq. RNA was used for detection of RET/PTC1 and RET/PTC3 rearrangements using Real Time PCR. Clinical and pathological data were compared between both cohorts. In the pediatric cohort, more aggressive categories T3 and T4 in TNM classification (47% vs 26.7%, P=0.001), significantly more frequent lymph node metastasis (73% vs 42%, P<0.001), extrathyroidal invasion (48.3% vs 29.9%, P=0.007) and angioinvasion (26.2% vs 14.0%, P=0.026) were present in comparison with adult PTC. The frequency of distant metastasis did not significantly differ between pediatric and adult PTC (4 vs 8.4%, P=0.304). Mutation in RAS genes was detected only in one patient - mutation Q61K in N-RAS gene (1,5% vs. 8% in adults, P=0.065), BRAF V600E mutation in nine pediatric patients (12.8% vs 37% in adult, P<0.001). No TERT mutations were found in pediatric PTC in contrast to 12% in adults (P=0.004). RET/PTC rearrangements were found in 14 patients (20.9% vs 5% in adults, P<0.001) nine RET/PTC1, five RET/PTC3 and one RET/PTC1ex9 were detected. RET/PTC1ex9 in 8 years old boy with aggressive classical variant of PTC (T4N1M1) was created by fusion of exon 1 of CCDC6 with exon 9 of extracellular domain of RET followed by exon 12 of RET. One 17 years old patient with T3N1M0 had BRAF V600E mutation together with RET/PTC1. In our cohort, PTC in pediatric patients presented more aggressive features than in adults, mainly with more advanced T in TNM classification, more frequent lymph node metastasis, extrathyroidal extension and angioinvasion. The molecular genetic analysis revealed that the prevalence of the RET/PTC fused genes was significantly higher in pediatric PTC compared with adult PTC, in contrast to significantly lower prevalence of the BRAF V600E and TERT mutations.
19 May 2018 - 22 May 2018