chronic lymphocytic leukemia

Last reviewed 08/2020

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).

  • although morphologically these cells are mature, immunologically they are less mature resulting in immunological compromise (1,2) 
  • most are clonal malignancies of B lymphocytes rather than T lymphocytes
  • it is manifested clinically by immunosuppression and bone marrow failure
  • in advanced disease, damage may occur from direct tissue infiltration by the lymphocytes.

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).

  • the 2008 International Workshop on Chronic Lymphocytic Leukaemia (IWCLL) has approved  the diagnosis of CLL in patients  with lower MBC counts but with cytopenias or symptoms attributable to the CLL. 
  • when the peripheral blood MBC count is < 5 x 109/l, the condition is referred to as monoclonal B lymphocytosis (MBL) (4)
  • when the peripheral blood MBC count is < 5 x 109/l and there is lymphadenopathy or splenomegaly because of infiltrating CLL cells the condition is known as small lymphocytic lymphoma (SLL) (5)

There may be some overlap between CLL and the leukaemic phase of lymphomas.