IDH1 and neoplasm: By contrast, arcade-like structures (Figure 5D) were restricted to IDH1 wild-type tumours (Figure 5E) (0/8 IDH1 mutant vs 48/262, 18%) (Figure 5D), which were also never observed in patients under the age of 40 years at diagnosis (0/12 vs 48/260, 18%, p = 0.09, Fishers exact test).