SDHD and pheochromocytoma: In a recent gene-expression study by Dahia et al. of sporadic, SDHB-, SDHD -, VHL-, MEN2- and NF1-associated phaeochromocytomas, two phaeochromocytoma clusters were identified: a cluster containing VHL-, and SDH- linked tumors and another containing MEN2- and NF1-linked tumors[9].