D2HGDH and cancer: Andreas von Deimling and coworkers, in particular Dr. Joerg Balss and Dr. Stefan Pusch, from the Clinical Cooperation Unit Neuropathology of the DKFZ (German Cancer Research Center) in Heidelberg (Germany) for kindly providing us with D-2-hydroxyglutarate-dehydrogenase (D2HGDH) and Dr. Stefan Pusch for revising the manuscript.