Haematogones in the peripheral blood of adults: A four-colour flow cytometry study of 102 patients

Haematogones have been extensively characterized in bone marrow, but not in the peripheral blood (PB). We studied 102 PB samples from adult patients with a sensitive flow cytometry method. Sixty-six of 102 samples (65%) contained detectable haematogones, ranging from 0.01% to 1.3% of white blood cells (median 0.06%, mean 0.13%). Of 66 cases with complete blood count data, 51 had absolute haematogone counts of 0.00037-0.105 × 10⁹/l (median 0.0054 × 10⁹/l, mean 0.012 × 10⁹/l). PB haematogones belonged exclusively to the most mature maturational stage. These findings have implications for PB analysis of minimal residual disease in acute lymphoblastic leukaemia and follicular lymphoma.