IMMUNOLOGICAL CLASSIFICATION OF ACUTE LYMPHOBLASTIC LEUKEMIAS

Abstract

Background. ALL is a malignant blood disease and lymphoblasts have origin in B or T lymphatic cell line. In 1997 established new World Health Organisation classification (WHO classification) of malignant haematological diseases realizes the importance of cellular immunological markers (immunophenotype) and chromosomal abnormalities (cytogenetics). Based on both findings we may distribute the patients in low, intermediate and high risk groups and the outcome of such distribution is risk adopted ALL treatment strategy. On Clinical department of haematology (CDH) we have decided to overview immunophenotype characteristics of all ALL patients during the January 1, 1995–December 31, 2001 period.

Methods and results. During the January 1, 1995–December 31, 2001 period on CDH we have treated 44 patients: 22 males and 22 females. With flow cytometer Coulter Epics XL MCS we have performed first primary antibody panel for acute leukemias antigens (CD2, CD7, CD10, CD19, CD34, cCD3, cCD13, cCD22, MPO, TdT), followed by secondary panel. The later have included antigen CD20, CD23, membrane and/or cytoplasmatic immunoglobulins or their light chains monoclonal antibodies for B-ALL and antigen CD3, CD4, CD5 and CD8 monoclonal antibodies for T-ALL subsets. Besides immunophenotyping we have evaluated all ALL patients also morphologically according to FAB classification (French-AmericanBritish classification), which is an old classification based solely on morphology.

32/44 (73%) patients have had immunophenotypic B-ALL, and 12/44 (27%) T-ALL. Subgroups distribution of B-ALL immunophenotype were: pro-B 4/44 (9%), »common«-B 18/44 (41%), pre-B 5/44 (11.5%) and mature B 5744 (11.5%) and for T-ALL immunophenotype were: pro-T 2/44 (4.5%), pre-T 5/44 (11.5%), cortical-T 4/44 (9%) and mature-T 1/44 (2%). Our results are quite comparable with the available data from the literature, despite the fact that newest immunological markers such as CD1a, CD79a and CD22 were not available until last year.

ALL morphology does not determine ALL immunophenotype, with the exception of L3 subtype, which usually coincidences with mature B immunophenotype. The commonest morphological variant is L2 subtype, which we have seen in 35/44 (80%) patients and was equally distributed among B and T immunophenotypic subgroups.

Conclusions. Determination of ALL immunophenotype is one of the cruical tests for the evaluation of long-term ALL prognosis. Because of the later, every newly diagnosed ALL must be immunophenotyped. Immunophenotype is not the only ALL prognostic factor, but in combination with the others such as cytogenetics, patients age, leukocyte count at diagnosis, we can put together »ALL prognostic mosaic«, followed by an optimal ALL treatment strategy.