CD4 and primary cutaneous T-cell non-Hodgkin lymphoma: Sézary syndrome (SS) is an aggressive, leukaemic cutaneous T‐cell lymphoma (CTCL) variant characterized clinically by severe erythroderma, pruritus and lymphadenopathy,1 and the presence of atypical, malignant Sézary cells in blood, lymph nodes and skin with CD3/CD4 expression and heterogeneous naïve/memory maturation phenotype.2