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Chronic lymphocytic leukaemia (CLL) arises from the neoplastic proliferation of relatively mature lymphocytes which progressively accumulate in the blood, bone marrow or lymphoreticular structures (1,2).
The 2008 WHO classification has modified the criteria for diagnosis of CLL from a chronic absolute lymphocytosis of > 5 × 10^9/L to an absolute count of > 5 x 10^9/l monoclonal B cells (MBC) with a CLL phenotype in peripheral blood (if there is an absence of disease-related symptoms or cytopenias, or tissue involvement other than BM). (4).
There may be some overlap between CLL and the leukaemic phase of lymphomas.