CD4, a member of the immunoglobulin superfamily, is a transmembrane glycoprotein, expressed on mature thymocytes, T-helper cells, the majority of mature peripheral T cells, and a subset of suppressor or cytotoxic T cells (1). In lymphoid tissue, CD4 expression can be found in the paracortical T zone. CD4+ T cells are also seen scattered in germinal center and mantle zone. CD4 is expressed in the majority of mature T-cell lymphomas (2). CD4 has been used in lymphoma panels that include CD3, CD5, CD8, CD7 and TIA-1 (2-3). A CD4 numerical assessment has been useful in HIV-infected individuals, as HIV infection depletes CD4+ T cells and has a strong association with the level of systemic CD4+ T cell activation (4). Tumor infiltrating CD4+ T cells may also be a prognostic factor for the strategy of early antitumor immunity (5).