Somatic mutations in PTEN, ARID1A, ATM, LRP1B, BRCA2 and NF1 did not show a preference for a particular primary tumour side, but were enriched in CMS1 tumours (Fig. 2h), and were associated with an increased tumour mutational burden (p = 0.008, p = 0.002, p = 0.017, p = 0.0001, p = 0.010 and p = 0.051, respectively, Fisher’s exact test). Here, ARID1A is linked to neoplasm.