Kaplan-Meier plots of survival by average MHC class II gene expression in PMBCL. (A) Cases were divided into the low 10% expressers (n = 4) versus the rest of the cases (n = 38). (B) Cases were divided into 4 approximately equal groups by expression (n = 10, 11, 10, 11 for increasing expression). Survival increases significantly and incrementally with increasing expression, P = .041 for the left graph, P = .039 for the right.