CLL

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.

Reference:

• (1) National Cancer Institute at the National Institutes of Health. Chronic Lymphocytic Leukemia Treatment. General information about chronic lymphocytic leukemia
• (2) Zenz T et al. From pathogenesis to treatment of chronic lymphocytic leukaemia. Nat Rev Cancer. 2010;10(1):37-50
• (3) British Committee for Standards in Haematology 2010. Best practice in lymphoma diagnosis and reporting - Specific Disease Appendix
• (4) Gibson SE et al. Reassessment of small lymphocytic lymphoma in the era of monoclonal B-cell lymphocytosis. Haematologica. 2011;96(8):1144-52
• (5) Campo E et al.The 2008 WHO classification of lymphoid neoplasms and beyond: evolving concepts and practical applications. Blood. 2011;117(19):5019-32
• (6) Redaelli A et al.The clinical and epidemiological burden of chronic lymphocytic leukaemia. Eur J Cancer Care 2004;13:279–287.