CD19 and myeloid sarcoma: Unstimulated CD19+ B cells from the two cohorts exhibited similarly low spontaneous TM rates (HC: 0.02 ± 0.01%; MS, relapse: 0.01 ± 0.01%; MS, remission: 0.03 ± 0.02% [migrated B cells as proportion of all B cells]; non-significant with p > 0.05 each) (Figure 4A).