Biased IGHV gene utilization observed in BL tumors. (A) Heat map illustrating IGHV gene usage in the 30 endemic BL samples from our cohorts, 40 published endemic BL samples, and 61 published sporadic BL samples, as compared with 42 healthy controls. Highly enriched IGHV genes are indicated in red, and genes with significant differential utilization (P < .05) in BL tumor and control B cells are indicated by an asterisk. Both IGHV gene utilization and all samples are clustered by similarity. (B) Frequency of IGHV gene utilization in the 5 significantly differentially used IGHV genes. IGHV gene frequencies in BL tumors are plotted in red, and IGHV gene frequencies of healthy controls are plotted in blue.