Single-cell atlas of malignant plasma cells (MPCs) from patients with MM. (A) Analysis of 17 599 MPCs color-coded using UMAP based on the cluster. (B) Proportion of MPCs in the BM and PB of 3 patients with MM. (C) Heatmaps of DEGs for each cluster in MPCs. (D) DEGs in MPCs from BM and extramedullary sites (ME + PB).