Clinical and Genetic Characteristics of Pheochromocytoma and Paraganglioma: A Single-Center Experience Including a Rare VHL Variant

<b>Background/Objectives:</b> Advances in the genetic understanding of pheochromocytoma-paraganglioma (PPGL) have considerably refined personalized approaches to diagnosis and management. This study aims to present our institutional experience on the diagnostic characteristics, clinical course, and genetic background of patients with PPGL, in the context of the current literature. <b>Methods:</b> This retrospective analysis included 35 patients diagnosed with PPGL between years 2020 and 2024, all of whom underwent surgical resection and next-generation sequencing for germline mutations in major PPGL susceptibility genes. Clinical presentation, biochemical profile, pathological findings, and follow-up outcomes were compared between mutation-positive and mutation-negative cases. <b>Results:</b> Of the 35 patients with PPGL, germline mutations were identified in 6 patients (17%): 2 in Cluster 1A genes (<i>SDHA</i>, <i>SDHB</i>), 2 in Cluster 1B (<i>VHL</i>), and 2 in Cluster 2 (<i>NF1</i>). Consistent with existing literature, pathogenic germline variants-particularly <i>SDHB</i> and <i>VHL</i>-were identified in our cohort exclusively in patients younger than 30 years (ages 17, 20, and 25). Mutation-positive patients more frequently exhibited noradrenergic or non-secretory profiles (<i>p</i> = 0.01). Among the three non-secretory tumors in the cohort, two harbored genetic mutations (<i>SDHA</i>, <i>NF1</i>). Interestingly, both <i>NF1</i>-positive patients were normotensive-one (<i>c.3496G > A</i>) with a non-secretory tumor and the other (<i>c.2329T > A</i>) presenting at an unusually late age (63 years)-a strikingly atypical spectrum that underscores the phenotypic variability of <i>NF1</i>-associated PPGL. Bilateral disease was observed exclusively in <i>VHL</i> carriers (<i>p</i> = 0.03). Importantly, we identified a rare <i>VHL c.369delG</i> frameshift variant, not previously reported in association with PPGLs, in a patient with PPGL. No significant difference was observed between SDHB loss (<i>p</i> = 0.1) and proliferative indices (mitotic count, Ki-67) (<i>p</i> = 0.07, <i>p</i> = 0.6) between the two groups. During a median follow-up of 24 months (IQR: 18-36), one <i>SDHB</i>-positive patient had a recurrence, while no distant metastases were detected in the remaining mutation carriers. <b>Conclusions:</b> These findings support characteristic clinical patterns among mutation-positive PPGL and underscore the importance of systematic germline testing in all cases-irrespective of age, family history, or biochemical profile-to guide individualized management and enable cascade screening. The identification of a rare <i>VHL c.369delG</i> variant, previously unreported in association with PPGL, within a characteristic VHL-related clinical phenotype highlights the importance of this association. Similarly, atypical <i>NF1</i> cases emphasize phenotypic variability and reinforce the importance of germline testing even in clinically silent presentations.