Acute leukemias of unclear differentiation line

The category of such leukemias include acute leukemias, in which neither morphological, nor cytochemical, nor immunophenotypic methods allow to establish the differentiation of blasts along any line of hemopoiesis (acute undifferentiated leukemia), as well as observations when morphological and / or immunophenotypic data indicate the presence signs of maturation along two lines of hemopoiesis: myeloid and lymphoid or B- and T-lymphoid (acute bilinear and acute bifenotypic leukemia).

In acute undifferentiated leukemia, the morphological and cytochemical indicators of the blasts do not have any characteristic features. Cells react only with µa to early hematopoiesis precursors – stem-cell CD34, contain the enzyme deoxynucleotidyltransferase (TdT), and also express the antigens CD38 and histocompatibility class II HLA-DR.

The First European Group on the Immunological Classification of Leukemia (EGIL) recommended that further studies of this undifferentiated variant be conducted to prove the myeloid or lymphoid pattern of cell differentiation. It is proposed to use a wide panel of 33 immunological markers. According to the authors, the study of blast cells should be carried out in 2 stages. First, it is necessary to study the linear non-specific antigens TdT, CD34, HLA-DR and establish B, T and myeloid linear directivity. Then it is necessary to determine the stage of differentiation of leukemic cells. To clarify the diagnosis, it is proposed to investigate the rearrangement of immunoglobulin genes and T-cell receptors.

Cases of undifferentiated acute leukemia are sometimes referred to as stem-cell. It has been established that the group of patients with such leukemia is heterogeneous according to the blasts phenotype. The following immunodvariants of this acute leukemia are distinguished: 1. CD34 +, HLA-DR-, CD38-; 2. CD34 +, HLA-DR +, CD38 ~; 3. CD34 +, HLA-DR \ CD38 +.