Absolute CD3+CD158k+lymphocyte count is reliable and more sensitive than cytomorphology to evaluate blood tumour burden in Sezary syndrome

P>Background CD158k/KIR3DL2 is a specific marker for Sezary cells which can be used to diagnose Sezary syndrome (SS) in erythrodermic patients with abnormal circulating T cells. Objectives To evaluate the suitability of CD158k/KIR3DL2 for detecting and evaluating blood tumour load during the follow up of patients with SS. Methods The absolute CD3+ CD158k+ lymphocyte count was compared with the absolute count of cytomorphological Sezary cells and was correlated with clinical flares in a cohort of patients with SS. Twenty-five patients were included in the study and 48 blood samples were analysed. Results The absolute count of CD3+ CD158k+ cells strongly correlated with the absolute count of atypical circulating cells (r = 0 center dot 97, P < 10-15). The CD3+ CD158k+ lymphocyte cell count was in eight cases more sensitive than cytomorphology for detecting atypical circulating cells especially for small-sized tumour cells. The tumour burden evaluated by CD3+ CD158k+ immunostaining was significantly associated with clinical flare (P < 10-4). Conclusions CD3+ CD158k+ phenotyping is a reliable and objective test to monitor the blood tumour burden in patients with SS under systemic therapy.