B2M and neoplasm: In this cohort, 29% of patients with MSI-H tumours harboured truncating mutations in B2M and about 7% of them have at least one mutation in JAK1 and JAK2. In addition, we identified 18.3% of MSI-H tumours carried loss-of-function mutations in PTEN that have been linked to the immunosuppressed tumour microenvironment [24].