Selective expression of syndecan-1 on myeloma cells.

Three-color fluorescence staining of BMMC in 2 representative patients with MM (Patient LC, panels A and C; and Patient FA, panels B and D) demonstrated expression of syndecan-1 on CD38⁻ (A, R1 region) and CD38^bright cells (B, R2 region). Gating of BMMC on syndecan-1⁺ cells (R1 and R2 regions) yielded the histograms shown in C and D. Expression of cytoplasmic monoclonal Ig (C,D) demonstrated that 95% of syndecan-1⁺/CD38⁻ (R1 region) and syndecan-1⁺/CD38⁺ (R2 region) BMMC were myeloma cells.