Chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) arises from the neoplastic proliferation of relatively mature lymphocytes which progressively accumulate in the blood, bone marrow or lymphoreticular structures (1,2,3).

• although morphologically these cells are mature, immunologically they are less mature resulting in immunological compromise
• 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)

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

References:

1. Eichhorst B, Robak T, Montserrat E, et al; ESMO Guidelines Committee. Chronic lymphocytic leukaemia: ESMO clinical practice guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2021 Jan;32(1):23-33.
2. Hallek M, Al-Sawaf O. Chronic lymphocytic leukemia: 2022 update on diagnostic and therapeutic procedures. Am J Hematol. 2021 Dec 1;96(12):1679-705.
3. Walewska R, Parry-Jones N, Eyre TA, et al. Guideline for the treatment of chronic lymphocytic leukaemia. Br J Haematol. 2022 Jun;197(5):544-57.
4. Campo E et al.The 2008 WHO classification of lymphoid neoplasms and beyond: evolving concepts and practical applications. Blood. 2011;117(19):5019-32