BTK and B-cell chronic lymphocytic leukemia: It could imply that M-CLL cases with high SLAMF1 or SLAMF7 expression derive relatively lesser benefit from BTK inhibition as compared to U-CLL (that is predominantly SLAMF1/SLAMF7 low) or the ~50% of M-CLL cases that downregulate SLAMF1/SLAMF7.