The molecular diagnostic criteria in CLL guidelines and beyond traditional Rai or Binet staging [21] include (i) the co-expression of CD5 with the B-cell antigens CD19 and CD20, (ii) characteristically lower levels of surface immunoglobulin, CD20, and CD79b (vs. normal B cells), (iii) the expression of kappa or lambda immunoglobulin (Ig) light chains [3,22] and (iv) the identification of specific gene mutations and serum markers [2,3,22,23]. Here, CD19 is linked to B-cell chronic lymphocytic leukemia.