B2M and B-cell chronic lymphocytic leukemia: Cochran’s Q test revealed heterogeneity in the associations of β2M with DLBCL (P = 2.00× 10−3), HL (P = 4.40 × 10−2), FL (P = 9.92 × 10−28) and CLL (P = 2.70× 10−2).