We discovered that 7 of 11 IDH1-mutated tumours were also ATRX-mutated (28-fold enrichment compared to IDH1 WT skin cancers; p = 1.2 × 10−8, Fisher’s exact test) and that both ATRX and IDH1 were predominantly hit by somatic mutations (14 of 15 for ATRX, 7 of 11 for IDH1). The gene discussed is IDH1; the disease is skin neoplasm.