We saw an statistically significant association between secondary glioblastoma phenotype and RASSF1A promoter methylation, as 4 of 5 tumors studied showed methylation of this gene; however, in the primary glioblastoma group, we could just detect 4 cases of methylation in 19 cases analyzed (Fisher's exact test, P = 0,028) (Figure 3). This evidence concerns the gene RASSF1 and glioblastoma.