Remarkably, SDHB IHC becomes negative most commonly in the setting where is bi-allelic inactivity in any of the four SDH subunit genes (SDHA, SDHB, SDHC, and SDHD) (26), and loss of function of both alleles almost always occurs in the presence of a germline mutation in PCC/PGL, but it can also occur in somatic mutation isolated to neoplastic cells (27). This evidence concerns the gene SDHB and adrenal gland pheochromocytoma.