The succinate dehydrogenase complex catalyzes the oxidation of succinate to fumarate; mutations in its subunits SDHA, SDHB, SDHC and SDHD, and in the assembly factor SDHAF2, result in syndromes with divergent tumor types, including pheochromocytoma/paraganglioma, gastrointestinal stromal tumor, and, less often, renal-cell carcinoma, pituitary adenoma24 ,and breast cancer26. The gene discussed is SDHB; the disease is pheochromocytoma.