In conclusion, we have shown that the [M-H]− and [M-H2O+H]+ adducts of 2HG could be detected and used to determine IDH mutational status both in frozen and FFPE samples and that aminoadipic acid and guanidinoacetic acid could be detected and used to evaluate the grade of astrocytomas both in frozen and FFPE samples. The gene discussed is IDH2; the disease is astrocytoma (excluding glioblastoma).