The ATRX (alpha thalassemia/mental retardation X-linked) gene is mutated in approximately 5% of all cancers with the highest incidence in glioblastoma, neuroendocrine pancreatic cancer (53% with mutations in DAX/ATRX), non-small lung carcinoma and sarcoma [98,113,114]. The gene discussed is ATRX; the disease is cancer.