B cell scRNA-Seq transcriptional profiles segregate into normal and malignant phenotypes. (A) TSNE analysis of 25 106 B cells across 11 samples reveals sample-specific and shared clusters of B cells in FLs (left), PBMCs (middle), and tonsils (right). Single cells are colored according to sample origin. Shared nearest-neighbor clustering of B cells in PC space identifies 10 clusters. Normal B cells (cluster 4 and 5) were abundant in the 5 control samples and detectable in all tumor samples. Each cluster is enclosed by kernel density estimates of the coordinates of its cell members (black polygons and adjacent numbers). (B) Cluster membership and sample origin of single cells point to 3 distinct cluster phenotypes: normal, cycling and quiescent. (C) Expression of 598 genes involved in cell cycle progression (Reactome-term “Cell cycle”) was highest in cluster 9. The scale shows the GSVA enrichment score¹⁹  per cell. (D) Fraction of B-cell subsets (λ⁺/ κ ⁺/ cycling), as estimated by scRNA-Seq (left) and flow cytometry (right). (E) Light chain restriction of “tumor” cluster groups in each sample show minimal contribution of nontumor cells, while the “normal” cluster group is heterogeneous.