CCND1 and neoplasm: To distinguish malignant B cells from nonmalignant B cells, we reclustered all B cells from each patient and annotated subclusters based on the expected features of tumor cells, including clonal BCR expression, a consistent ratio of immunoglobulin (Ig) kappa to lambda light chain (IGK/IGL), and CCND1 overexpression (exemplified by MC206, Figures S1A–S1E).