Comprehensive Genomic Analysis in Hereditary Adrenal and Extra-Adrenal Paragangliomas

Adrenal and extra-adrenal paragangliomas (PPGLs) are highly heritable non-epithelial neuroendocrine neoplasms. Through a retrospective chart review of 110 individuals diagnosed with PPGLs at the University Health Network in Toronto, Canada (2011-2023), we characterized germline findings, tumor features, self-reported ethnicity, and variant reclassification across a multi-ethnic cohort using targeted germline panel sequencing, whole genome sequencing (WGS), and optical genome mapping (OGM). Panel sequencing identified pathogenic or likely pathogenic (P/LP) germline variants in 28.18% (31/110) of individuals, with five variants of uncertain significance (VUS) in PPGL predisposition genes reclassified to P/LP during the study period (32.7%, 36/110). VUS rates were comparable across ethnic groups (16.28%, 7/43 in the group of non-European ethnicities; 17.24%, 10/58 in the group of European ethnicities), but the non-European group had a lower rate of VUS-to-P/LP reclassification (28.57%, 2/7 vs. 40.0%, 4/10). Uninformative targeted panel testing was supplemented by WGS in seven individuals with succinate dehydrogenase (SDH)-deficient tumors, leading to detection of P/LP in 6/7 cases (85.7%). Broader sequencing also uncovered incidental P/LP variants in genes without an established PPGL association, including TSC1 and PALB2. OGM resolved a complex structural variant (SV) involving SDHA as an inverted tandem duplication that WGS alone could not fully characterize. Our findings support a tiered diagnostic approach: comprehensive germline panels and tumor SDHB immunohistochemistry to maximize solved cases, with WGS and OGM reserved for select unresolved cases, and highlight the importance of equitable variant interpretation across diverse PPGL populations.