Targets expressed in normal bone marrow plasma cells can be divided in those in which expression in myeloma cells remains stable in later stages in longitudinal samples (i.e., CD38, CS1, BCMA, FCRH5, CD74, CD79B), and those for which expression is stage-dependently lost (e.g., CD19, CD22, BAFF-R). The gene discussed is CD19; the disease is plasma cell myeloma.