In the diffuse astrocytoma, we show that the germline CDKN2A/B deletion was accompanied by somatic loss of the remaining CDKN2A/B alleles as well as an activating hotspot mutation in PTPN11 and inactivating frameshift mutations in the ATRX and NF1 tumor suppressor genes. This evidence concerns the gene PTPN11 and diffuse astrocytoma.