Hierarchical clustering of MMCs, BMPCs, and PPCs identifies a signature of BM stroma interaction for TACI^hi patients and a plasmablastic signature for TACI^lo patients. Unsupervised hierarchical clustering analysis of the expression profile of MMCs of 65 patients at diagnosis, 7 PPC samples, and 7 BMPC samples show that TACI^lo MMCs cluster (blue) together with PPCs (yellow) whereas TACI^hi MMCs cluster (red) with normal BMPCs (purple). The clustering was performed on the 659 genes differentially expressed between TACI^hi and TACI^lo MMCs. The TACI₄₀^lo, TACI₂₅^lo, and TACI₁₅^lo subgroups were represented by graded blue color (more intense in TACI₁₅^lo) and the TACI₄₀^hi, TACI₂₅^hi, and TACI₁₅^hi subgroups with graded red color (more intense in TACI₁₅^hi).