Pheochromocytoma and Paraganglioma: Genetics, Diagnosis, and Treatment

Silent genetic alterations identified by targeted next-generation sequencing in pheochromocytoma/paraganglioma: A clinicopathological correlations

AIMS

The goal of this pilot study was to develop a customized, cost-effective amplicon panel (Ampliseq) for target sequencing in a cohort of patients with sporadic phaeochromocytoma/paraganglioma.

METHODS

Phaeochromocytoma/paragangliomas from 25 patients were analysed by targeted next-generation sequencing approach using an Ion Torrent PGM instrument. Primers for 15 target genes (NF1, RET, VHL, SDHA, SDHB, SDHC, SDHD, SDHAF2, TMEM127, MAX, MEN1, KIF1Bβ, EPAS1, CDKN2 & PHD2) were designed using ion ampliseq designer. Ion Reporter software and Ingenuity® Variant Analysis™ software (www.ingenuity.com/variants) from Ingenuity Systems were used to analysis these results.

RESULTS

Overall, 713 variants were identified. The variants identified from the Ion Reporter ranged from 64 to 161 per patient. Single nucleotide variants (SNV) were the most common. Further annotation with the help of Ingenuity variant analysis revealed 29 of these 713variants were deletions. Of these, six variants were non-pathogenic and four were likely to be pathogenic. The remaining 19 variants were of uncertain significance. The most frequently altered gene in the cohort was KIF1B followed by NF1. Novel KIF1B pathogenic variant c.3375+1G>A was identified. The mutation was noted in a patient with clinically confirmed neurofibromatosis. Chromosome 1 showed the presence of maximum number of variants.

CONCLUSIONS

Use of targeted next-generation sequencing is a sensitive method for the detecting genetic changes in patients with phaeochromocytoma/paraganglioma. The precise detection of these genetic changes helps in understanding the pathogenesis of these tumours.

Pediatric patients with pheochromocytoma and paraganglioma should have routine preoperative genetic testing for common susceptibility genes in addition to imaging to detect extra-adrenal and metastatic tumors

BACKGROUND

Pediatric pheochromocytomas and paragangliomas are rare with limited data on the optimal management approach. The aim of this study was to determine the role of genetic testing and imaging to detect extra-adrenal and/or metastatic tumors in pediatric pheochromocytomas and paragangliomas.

METHODS

We performed a retrospective study of 55 patients diagnosed at ≤21 years of age with pheochromocytomas and paragangliomas with analysis of data on genetic testing and multimodal imaging.

RESULTS

Eighty percent of patients (n = 44/55) had a germline mutation. The majority were found to have either VHL (38%) or SDHB (25%) mutation. Pheochromocytoma was present in 67% (n = 37/55) of patients and was bilateral in 51% (n = 19/37). The majority of patients with bilateral pheochromocytomas had VHL (79%). Abdominal paragangliomas was present in 22% (n = 12/55), head and neck paragangliomas in 11% (n = 6/55), and thoracic paragangliomas in 2 of 55 patients. For paragangliomas, SDHx accounted for 72% (n = 13/18) of mutations. The rate of malignancy was 16% (n = 9/55), 56% of whom had SDHB mutations. In two-thirds of patients, functional imaging identified either extra-adrenal paragangliomas and/or metastatic disease.

CONCLUSION

The majority of pediatric patients with pheochromocytomas and paragangliomas have detectable germline mutations. Therefore, we suggest strongly that all pediatric patients with pheochromocytomas and paragangliomas undergo genetic testing and imaging to detect extra-adrenal paragangliomas and metastatic disease to guide treatment and follow-up.

Genetic associations with neuroendocrine tumor risk: results from a genome-wide association study

The etiology of neuroendocrine tumors remains poorly defined. Although neuroendocrine tumors are in some cases associated with inherited genetic syndromes, such syndromes are rare. The majority of neuroendocrine tumors are thought to be sporadic. We performed a genome-wide association study (GWAS) to identify potential genetic risk factors for sporadic neuroendocrine tumors. Using germline DNA from blood specimens, we genotyped 909,622 SNPs using the Affymetrix 6.0 GeneChip, in a cohort comprising 832 neuroendocrine tumor cases from Dana-Farber Cancer Institute and Massachusetts General Hospital and 4542 controls from the Harvard School of Public Health. An additional 241 controls from Dana-Farber Cancer Institute were used for quality control. We assessed risk associations in the overall cohort, and in neuroendocrine tumor subgroups. We identified no potential risk associations in the cohort overall. In the small intestine neuroendocrine tumor subgroup, comprising 293 cases, we identified risk associations with three SNPs on chromosome 12, all in strong LD. The three SNPs are located upstream of ELK3, a transcription factor implicated in angiogenesis. We did not identify clear risk associations in the bronchial or pancreatic neuroendocrine subgroups. This large-scale study provides initial evidence that presumed sporadic small intestine neuroendocrine tumors may have a genetic etiology. Our results provide a basis for further exploring the role of genes implicated in this analysis, and for replication studies to confirm the observed associations. Additional studies to evaluate potential genetic risk factors for sporadic pancreatic and bronchial neuroendocrine tumors are warranted.

Metastatic Paraganglioma Presenting as Incontinence in a 15-Year-Old Girl

Chromaffin cell tumors are derived from neural crest cells and can produce and secrete catecholamines. Classic symptoms include headache, palpitations, diaphoresis, and hypertension. Diagnosis is typically in adulthood, and metastatic disease is rarely found. Genetic testing is suggested with young age, extra-adrenal tumors, malignant disease, or family history of associated tumors. Our young patient's presentation of incontinence is unique, but several other atypical findings can be accounted for relative to her germline mutation. Because of the rarity of our patient's case, follow-up procedure is undefined. Documenting atypical cases such as this is central to clinician awareness and development of follow-up protocol.