CDKN2A and anaplastic astrocytoma: Homozygous deletion of CDKN2A (encoding p16INK4a) can be observed with low frequency in paediatric LGG [175], but is more common in higher‐grade tumours, such as pleomorphic xanthoastrocytoma and anaplastic astrocytoma with piloid features, suggesting that it probably acts as a second oncogenic hit, promoting senescence escape and facilitating transformation into high‐grade glioma [176, 177.