CD4 is a transmembrane glycoprotein, expressed on normal thymocytes, T-helper cells, the majority of mature peripheral T cells, and a subset of suppressor or cytotoxic T cells (1). Like many cell surface receptors/markers, CD4 is a member of the immunoglobulin superfamily. CD4 is expressed in the majority of T-cell lymphomas, including mycosis fungoides (2). CD4 has been used in lymphoma panels that include CD3, CD5, CD8, CD7 and TIA-1 (2-3). A panel consisting of CD4(+), CD2(-) and CD56(+) antibodies was also used to help identify agranular natural killer cell lymphoma of the skin (4). A CD4 assessment may be useful in HIV-infected individuals, as HIV infection depletes intestinal CD4(+) T cells and has a strong association with the level of systemic CD4(+) T cell activation (5). Tumor infiltrating CD4 T cells may also be a prognostic factor for the strategy of early antitumor immunity (6).