single-cell RNA sequencing (scRNAseq), multiple myeloma (MM), monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), single-cell B cell receptor sequencing (scBCR-seq), plasma cells (PCs), intra-tumoral heterogeneity (ITH), tumor microenvironment (TME), hyperdiploid (HY), non-hyperdiploid (non-HY)