CD4 and neoplasm: Regulatory T cells (Tregs) are a unique immunosuppressive subset of CD3+CD4+ T helper lymphocytes present in the tumour microenvironment (TME); they express specific biomarkers, such as CD4, CD25 and Foxp3 (forkhead box protein 3) and are thought to be derived from the same lineage as naïve CD4+ cells.