MON-218 Clinical and Genetic Aspects of Pediatric Pheochromocytomas and Paragangliomas

Pheochromocytomas and paragangliomas (PPGLs) are neuroendocrine tumors derived from chromaffin cells. At least 30% of PPGL patients have hereditary predisposition. PPGLs in children are more often hereditary, multiple and extra-adrenal. To date, more than 14 tumor-susceptibility genes have been reported: Cluster 1 or hypoxic (VHL, SDHB, SDHD, SDHC, SDHA, SDHAF2, FH, ENGL1 and HIF2A) and cluster 2 (RET, NF1, TMEM127 and MAX). The aim of this study was to evaluate clinical and molecular aspects of a Brazilian cohort of pediatric patients with PPGLs. Out of 262 patients with PPGLs, 26 (9 %) were diagnosed before 19 yrs of age (16 males and 10 females), with a median age of 14.5 yrs (range, 4 to 18). Genetic investigation was performed in 19 patients: 14 by automated Sanger sequencing (VHL, SDHB, SDHD and RET genes) and 5 by a custom next-generation sequencing (NGS) panel including all genes previously associated with germline mutations in PPGLs. Median tumor size was 5.5 cm (1.7 to 16). Pheochromocytomas (PHEOs), paragangliomas (PGLs) or both were diagnosed in 46%, 31% and 23% of the patients, respectively. Bilateral PHEOs were diagnosed in 61% of the cases, most of them asynchronous (75%). Genetic diagnosis was confirmed in 14 out of 19 (74%) patients and all variants were found in heterozygous state: 8 VHL missense mutations from 6 kindreds (p.R167W in 2 kindreds, p.R167Q in one and p.G114S in 3); 3 SDHB mutations (p.C98Y, c.201-2A>G and p.L180L); 2 SDHD mutations (p.Y144_H145del and p.Q121*); and one RET mutation (p.C634R). All 8 VHL patients had bilateral PHEOs and 3 of them had also abdominal PGLs. All patients with SDHB mutations had abdominal PGLs. Two patients with SDHD mutation had head and neck paraganglioma (one of them had unilateral PHEO). Genetic investigation by NGS Panel was negative in all 5 cases: 2 malignant PPGLs (one PHEO and one PGL) and 3 PHEOs. Four out of 26 (15%) pediatric PPGLs were malignant: 2 with SDHB mutation and 2 with negative screening (one PHEO and one PGL). In conclusion, the majority of pediatric PPGLs (74%) were hereditary and almost exclusively caused by mutations in hypoxic genes. VHL (PHEOs) and SDHB (only PGLs) were the most frequent affected genes in this cohort of pediatric PPGLs. Support: CAPES grant to Petenuci J.