Aims: Cutaneous T-cell lymphomas (CTCL) are a group of lymphomas comprising Mycosis Fungoides (MF) and Sézary syndrome (SS) which is characterized by erythroderma and high numbers of atypical lymphocytes. A blood classification was added to TNM staging and flow cytometry (FCM) became a promising method. We have shown the reliability of KIR3DL2 as a positive marker for SCs. We report our 4 years expertise for initial diagnosis in 219 patients.
Methods: CD7, CD26, and KIR3DL2 labelling was performed. Patients were diagnosed according to the ISCL/EORTC classification for CTCL. We gathered the samples at diagnosis for 31 SS, 5 pre-SS, 45 MF, 12 EMF and 126 patients with inflammatory skin diseases (ISD). 2 groups of patients were defined, according to their CD4+T-cell absolute counts: group A (≥1000/mm3) and group B (<1000/mm3).
Results: A strong positive correlation between KIR3DL2+ and CD4+CD26-T-cell count was found in group A (r=.81, p<.0001). A value of KIR3DL2+T-cells ≥200/mm3 allowed a specificity of 90% and a sensitivity of 86% for SS diagnosis. In group B, all patients with KIR3DL2+ T-cells ≥200/mm3 were SS. Five patients initially diagnosed as MF or pre-SS developed SS within 2-7 months. These patients already displayed >200/mm3 KIR3DL2+ at initial time point.
Conclusion: the detection of KIR3DL2+T-cells improves the biological diagnosis of SS. A threshold value of KIR3DL2+ cells ≥200/mm3 in MF and pre-SS patients with CD4 lymphopenia may be predictive for SS evolution. We therefore recommend to use this marker for the initial diagnosis and staging of CTCL, in association with CD26.