Monoclonal B-cell lymphocytosis (MBL), an essential precursor to chronic lymphocytic leukemia (CLL), is a surprisingly common finding in healthy blood donors, thus raising concerns about the potential risk infusion of these blood products may present to recipients.
MBL is defined as <5000 monoclonal B cells per μL of blood and no lymph node involvement. Low-count MBL (low risk of development of CLL, although risk may be affected by other factors) has <500 cells per μL and clinical MBL (increased risk of CLL) has >500 cells per μL. SLL, small lymphocytic leukemia. Professional illustration by Marie Dauenheimer.
Monoclonal B-cell lymphocytosis in donors
Image credits: ASM image library