Dark brown, solid tumor arising in the adrenal medulla. Bright yellow normal adrenal cortex can be seen to the left of the tumor. Several genes have been linked to pheochromocytomas and paragangliomas. They include: RET (MEN-2a, Sipple syndrome; MEN-2b, Gorlin syndrome); NF1 (Neurofibromatosis, type 1); VHL (von Hippel-Lindau disease); mitochondrial succinate dehydrogenase subunit B, C, and D genes SDHB, SDHC, SDHD (Familial Pheochromocytoma-Paraganglioma syndrome). Germline mutations in one of these 6 genes are seen in about 25% of cases of pheochromocytomas and paragangliomas. Patients are usually younger than those with sporadic tumors and harbor bilateral disease in as many as 50% of cases. Image copyright: pathorama.ch.