The results indicated that patients with concomitant CLL and MPN usually present indolent CLL course with good prognostic factors (mutated immunoglobulin variable (IgVH) region in 70% of cases, negativity of CD38 and Zap-70 expression in 78.5% and 71%, respectively, and a low-risk FISH karyotype (normal, +12, or del13q14) in 92.8% of the evaluable cases). The gene discussed is CD38; the disease is myeloproliferative neoplasm.