Phaeochromocytoma and paraganglioma: Next-generation sequencing and evolving Mendelian syndromes

The clinical and molecular investigation of familial neoplasia has provided important insight into the molecular mechanisms of neoplasia and enhanced the clinical management of affected individuals and their at-risk relatives across a broad range of human neoplasias. For most tumour types, only a small minority (typically up to 10%) of cases will occur in individuals with a high- or moderate-penetrance Mendelian disorder, but this proportion is much higher in patients with phaeochromocytoma and paraganglioma (PPGL). Thus, although the traditionally taught ‘10% rule’ suggests that only 10% of cases of PPGL are familial, it is now recognised that at least 25% of apparently sporadic cases of PPGL have a genetic basis.1,2

Currently, germline mutations in 12 genes are known to be associated with inherited PPGL, and it is likely that this number will increase. The genes and associated clinical features are summarised in Table 1, which highlights that the precise type of PPGL and the nature of other associated tumours vary according to the specific gene involved. The three longest recognised genetic causes of predisposition to PPGL are neurofibromatosis type 1 (NF1, von Recklinghausen's disease), multiple endocrine neoplasia 2 syndrome types A and B (MEN2A and MEN2B) and von Hippel–Lindau (VHL) disease.