Genetic analysis in longitudinal samplesa.

aGenetic alterations of six tumor-related gene in paired oligodendroglial tumors. “1st” and “2nd” indicate the primary (at initial diagnosis) and secondary (after progression) resections, respectively. Diagnoses in bold indicate patients who experienced progression in tumor grade or to a more aggressive phenotype between the first and second resections. Patients with a single diagnosis are those who did not experience progression in tumor grade or phenotype, but whose diagnosis remained stable from the first to the second resection. “DEL”s indicate samples for which chromosomal deletion was observed, and “RET”s indicate samples for which retention of both chromosomal alleles was observed. “mut” = mutated IDH1; “wild” = wild type IDH1.