B2M and neoplasm: Deleterious B2M mutations lead to loss of HLA class I expression, which allows tumour cells to avoid recognition by cytotoxic T lymphocytes but activates natural killer (NK) cells to destroy tumour cells in circulation, as a result of missing ‘self‐recognition’.13, 15, 17, 22 There is growing evidence that HLA class I‐deficient tumour cells are less likely to establish distant metastases than HLA class I‐proficient cells.