The value of five blood markers in differentiating mycosis fungoides and Sézary syndrome: a validation cohort

BACKGROUND Clinical and histological diagnosis of Sezary syndrome (SS) and mycosis fungoides (MF) is challenging in routine. We investigated five blood markers previously described for SS (T-plastin, Twist, KIR3DL2, NKp46 and Tox) in a prospective validation cohort of patients. METHODS The markers were analyzed by RT-q-PCR on peripheral blood leucocytes and CD4+ T-cells in a cohort of consecutive patients with early MF, erythrodermic MF and SS and compared to patients presenting with benign inflammatory dermatoses (BID) and erythrodermic BID. The markers were assessed in parallel to gold standard values such as CD4/CD8 ratio, loss of CD7 and CD26 membrane expression, and CD4 absolute values. Sensitivity and specificity were analyzed by Receiver Operator Characteristics curves. The prognostic value of selected markers was analyzed on a subset of patients. RESULTS We included 447 patients in this study and 107 patients were followed up for prognosis. We defined cutoffs for each marker. T-plastin, Twist and KIR3DL2 had the best validity. This study was conducted in one center. SS may be overrepresented. The combination of T-plastin and Twist was able to differentiate between erythrodermic MF or BID and SS. The additional analysis of KIR3DL2 may be useful to predict the prognosis. CONCLUSION We propose T-plastin, Twist and KIR3DL2 measured by RT-q-PCR as new diagnostic markers for Sezary syndrome.