CD4 and neoplasm: Tumours characterised with microsatellite instability (MSI) associated with hyper mutation and hyper methylation patterns, an enrichment for BRAFV600E mutations, and a high immune cell infiltration (CD8+ cytotoxic T lymphocytes, CD4+ T helper 1 (TH1) cells and natural killer (NK) cells) in the tumour microenvironment are classed within CMS1 [21,22].