IDH1 mutation, a genetic alteration associated with adult gliomatosis cerebri

Recently, mutations in IDH1 and IDH2 have been reported as an early and common genetic alteration in diffuse gliomas, being possibly followed by 1p/19q loss in oligodendrogliomas and TP53 mutations in astrocytomas. Lately, IDH1 mutations have also been identified in adult gliomatosis cerebri (GC). The aim of our study was to test the status of IDH1/2, p53 and of chromosomes 1 and 19 in a series of 12 adult and three pediatric GC. For all tumors, clinico-radiologic characteristics, histopathologic features, status of IDH1/2, p53 and of chromosomes 1 and 19 were evaluated. IDH1 mutations were detected only in GC of adult patients (5/12). They all corresponded to R132H. Additional 1p/19q losses were observed in two of them with histological features of oligodendroglial lineage. Other copy number alterations of chromosomes 1 and 19 were also noticed. The median overall survival in adults was 10.5 months in non-mutated GC and 43.5 months in mutated GC. IDH1 mutations were present in GC of adult patients, but not in those of children. There was a trend toward longer overall survival in mutated GC when compared to non-mutated ones. Concomitant 1p/19q loss was observed in IDH1-mutated GC with oligodendroglial phenotype. These observations contribute toward establishing a stronger link between GC and diffuse glioma. In addition, these results also emphasize the importance of testing for IDH1/2 mutations and 1p/19q deletions in GC to classify them better and to allow the development of targeted therapy.