[Expression of proliferation marker Ki 67 in chronic lymphocytic leukemia]

Chronic lymphocytic leukemia (CLL) is characterized by a clonal expansion of low proliferating mature B and T lymphocytes in the bone marrow and peripheral blood. The nuclear antigen Ki 67 is a protein detected in G1, S, G2 and M phases of the cell cycle, but not in G0, and thus, is a widely accepted proliferation marker of Human tumors. The aim of this study was to evaluate Ki 67 monoclonal antibody in CLL. We studied 48 patients diagnosed as CLL on the presence of clinical signs, over 4.109/l circulating lymphoid cells and immunophenotyping by flow cytometry using CD19, CD5, CD22, CD23, FMC7 and immunoglobulin light chains monoclonal antibodies. Ki 67 immunostaining was determined by Avidin Biotin Complex method. Our results allows to characterize between CLL: one group which proliferation rate (percentage of Ki 67 positive cells) was equal or less than 2%, represented by 14 cases (29,2%) with morphological aspect of typical CLL, one group which proliferation rate was between 3% and 9% represented by 32 cases (66,6%) with morphological aspect of polymorph CLL or prolymphocytic leukemia, and a last group with proliferation rate equal or up to 10% and corresponding to two cases (4,2%) of transformation of CLL to high grade Non Hodgkin lymphoma. There were no correlation between Matutes immunological score and proliferation rate, as this rate was 2.9% in score < 3 and 2.7% in score > 3. This study confirm the Ki 67 usefulness in studying cellular proliferation, and underline that CLL with polymorphic cytology are more proliferate than typical CLL. These data reinforce the notion that CLL is a disease with heterogeneity in clinical behavior, immunophenotype, cytogenetic, molecular aspects, and thus, prognostic.