SDC1 and cancer: In addition, the plasticity of the 5TGM1 cells under these experimental conditions and the fact that 89% of GFP+DiDhi cells are CD138+ suggests that dormant myeloma cells are distinct from cancer stem cells, which are thought to be poorly differentiated cancer cell precursors41, and the myeloma stem cell, which have been reported to be CD138neg (refs 42, 43).