SDHB and kidney neoplasm: Although rare renal tumors with mutations in other subunits of the SDH complex (49, 50) or negative SDHA staining (47) have been reported, in general it appears that defects in any of the subunits destabilize the enzyme complex, resulting in abnormal negative SDHB staining regardless of which gene harbors the mutation (51), making SDHB a useful screening immunohistochemical marker.