MT-ND1 and neoplasm: While all three genes appear to be expressed more highly in SDHB- than VHL-derived PHEOs/PGLs, ND1 and Uqcrc1 expression appears to be decreased in VHL-derived tumor tissues and close to normal in SDHB-derived PGLs, while CO1 is elevated in SDHB-derived PGLs compared to normal medulla and VHL-derived PHEOs.