There are still a lot of unanswered questions about these ALT mechanisms, mainly the ones regarding the molecular basis of its activation in tumour cells with wildtype ATRX or DAXX. The tumours with higher prevalence of ALT are reported as the least TERTp-mutated types, with the exception of gliomas (including WHO grades II–IV diffuse astrocytic and oligodendroglial tumours), in which a high frequency is observed for both mechanisms of cell immortalization. This evidence concerns the gene ATRX and neoplasm.