Clinicopathological and genomic analysis of pediatric pheochromocytoma and sympathetic paraganglioma.

Pediatric patients with pheochromocytoma (PCC)/paraganglioma (PGL) (PPGL) are rare, and clinicopathological investigations, especially the relationship between gene analysis and histological features, are insufficient. We comprehensively examined the clinical data, germline/somatic variants (mutations), and pathological characteristics of operated tumors using immunohistochemical expression and histological grading by Grading of Adrenal PCC and PGL score. This study included 28 patients (15 males and 13 females) aged <19 years. The age at the diagnosis was 12.8 ± 4.5 years. The included patient often had multiple PPGLs, with 39 tumors, including 21 PCCs and 18 PGLs, with average tumor sizes of 45.0 ± 22.8 and 42.6 ± 23.6 mm, respectively. Genomic types examined by gene mutations and immunohistochemistry of CA9 for VHL, SDHB for SDHx, and MAX for MAX, classified them into 14 VHL (50%), ten SDHx (35.7%), one MAX (3.6%), and three unknown (10.7%) types. Tumor metastasis was limited to two SDHB-related PPGLs, but not to VHL-related PPGLs. In both patients, the metastatic sites were the bones. The average GAPP score of the PPGLs was 2.9 ± 1.5 in VHL and 5.3 ± 1.7 in SDHB, and histological grades were well-differentiated in VHL and moderately differentiated in SDHB. SSTR2 expression was positive in 90% of SDHB-related PPGLs, but negative in 75% and weakly or focally positive in 25% of VHL-related PPGLs. Most pediatric PPGLs (90%) demonstrated mutations in VHL, SDHB, and MAX, with histological features depending on the mutation type. Combined genetic and immunohistochemical examination is desirable for accurate genomic diagnosis, and clinicopathological study.