IHC expression of class IA PI3K isoforms in mantle cell lymphoma. (A) Dot plot showing expression of class IA isoforms in MCL biopsies (144 biopsies evaluable for all 3 isoforms from 109 patients) compared with tonsil controls (n = 14). Each dot represents the average IHC score of triplicate cores and bars represent median expression. P110δ is highly expressed in MCL and p110α shows a wide range of expression, whereas p110β expression is the weakest. (B) Dot plots showing significant increase in p110α expression, but not p110β or p110δ, beyond first relapse. (C) This finding is more striking in 12 sequential cases, 6 of whom had biopsies beyond first relapse (connected by gray lines). (D) Representative IHC images (original magnification ×200) of sequential biopsies from 2 patients showing a significant increase in p110α expression with relapse *P < .05, **P < .01. ns, not significant.