Characteristics Of Chronic Lymphocytic Leukemia (CLL) In Senegal. Clinical Features, Cytology, Immunophenotype, Cytogenetic Abnormalities and Altered Expression Of Micro-RNA

The incidence of CLL in Africa is not known for several reasons, among them the difficulty to access the diagnosis since there is only clinical features and cytology which are available in several countries in francophone Africa, especially in Senegal. The WHO criteria which have been published since 2001 from the first revised WHO classification of tumours of haematopoitic and lymphoid tissues cannot be applied since there is no facility for immunophenotyping and cytogenetic. Moreover, no research in place can be set up without any precise diagnosis.

In this study, we have developed the flow cytometry technique in the laboratory of Immunology in CHU Le Dantec in Dakar to obtain the immunophenotype looking at the expression of Kappa/lambda light chains, CD19, CD22, CD20, FMC7, CD5, CD10, CD23, CD38. Peripheral blood smears were fixed according to the technique for FISH to detect the following cytogenetic abnormalities: trisomy12, deletion 13q14, deletion 11q22-23, deletion 17p. RNA to test by qRT-PCR the expression of microRNA mir15a, mir16-1, mir181a, mir181b, and mir 34a and 34b was obtained from peripheral blood lymphocytes.

Twelve cases of CCL aged ranging from 50 to 80 year old were characterized at clinical level according to the Binet’s system: 1 stage A, 5 stage B, 6 stages C. In most of cases (9 cases) hyperlymphocytosis of small lymphocytes with clumped chromatin and scanty cytoplasm was very high (122.000 to 336 000/mm3). The “Matutes” score obtained by immunophenotyping was 5 or 4 for 11 patients in favor of typical CLL. The expression of CD38 which is a marker of unfavorable prognosis is positive in 9 patients. Nine patients had cytogenetic abnormalities: 3 trisomy 12, 6 del 13q14, 2 del 11q22-23, 1 del17p. Four patients had two simultaneous cytogenetic abnormalities (tri 12, tri 13 ; del13q14, del11q22-23 ; del13q24, del17p ; del13q24, tri12).

The analysis of mi-RNA showed high expression of mir15a and mir 16-1 and low value of mir181a and mir 181b which were described in aggressive CLL ; however the expression of mir 34a and mir34b was also high.

This study shows the aggressiveness of CLL in Senegal, probably due to the delay of the diagnosis. We have also demonstrated the possibility to set up immunophenotype and the possibility of a precise diagnosis of lymphoproliferative disorder in place, in western Africa and the series will be extended. Moreover we have also demonstrated the possibility to construct translational research project from samples characterized in the University Hospital in Dakar gathering the cases from different sanitary structures in the country.

Such experiment would be a model for epidemiologic, clinico-biologic and translational research studies in order to set up in the country the capacity building for diagnosis and research.