Differential diagnosis, such as CLL with plasmacytic differentiation and CD5+ lymphoplasmacytic lymphoma, were excluded due to: i) the clear presence of two distinct malignant populations; ii) the absence of CD138 expression on CLL lymphocytes and the expression of IgD on the surface of the CLL lymphocytes, unlikely lymphoplasmacytic phenotype; iii) detection of IgG instead of IgM paraprotein in the plasma of the patient [15]. The gene discussed is SDC1; the disease is B-cell chronic lymphocytic leukemia.