CD4 and lymphoma: In WHO-HAEM4R, primary cutaneous gamma/delta T-cell lymphoma, CD8-positive aggressive epidermotropic cytotoxic T-cell lymphoma, acral CD8-positive T-cell lymphoproliferative disorder and CD4-positive small or medium T-cell lymphoproliferative disorder were grouped together under the term ‘cutaneous peripheral T-cell lymphoma, rare subtypes’, but are now each listed as separate entities in WHO-HAEM5 acknowledging their specific clinicopathological and genetic characteristics.