High Expression of Fas/CD95 on CD4+ Circulating T Cells: An Exclusion Criterion in the Diagnosis of Mycosis Fungoides?

The aim of this 10-year monocentric prospective study was to determine a cut-off value of Fas/CD95 expression by peripheral blood CD4+ T lymphocytes in discriminating patients with mycosis fungoides from controls with cutaneous benign lymphocytic conditions. CD95 expression in peripheral blood CD4+ T lymphocytes was measured using flow cytometry in 330 patients referred for diagnosis: 104 with mycosis fungoides and 226 with eczema, psoriasis, drug reaction, etc. The sensitivity and specificity of different thresholds of CD95 expression were calculated regarding the final diagnosis of patients with mycosis fungoides or controls. CD95 expression higher than 30% reached a specificity of 91% in ruling out a diagnosis of mycosis fungoides, although overall CD95 expression was not significantly different from that of controls (p = 0.309) and sensitivity was very low (5%). Thus, peripheral CD95 expression higher than 30% could be used among the exclusion criteria in a multicomponent score for mycosis fungoides diagnosis.