Modern diagnosis of acute leukemia
The basis for the modern diagnosis of acute leukemia was the FAB classification proposed in 1976 by a group of French, American and British hematologists. This classification is based on the criteria obtained in the morphological and cytochemical study of normal and leukemic cells. The morphocytochemical approach made it possible to diagnose most cases of AML: acute myeloblastic, promyelocytic, monoblastic leukemia, and erythromyelosis.
A comparative analysis of the morphological features of leukemic blasts allowed us to establish the signs of myeloid differentiation: graininess in myeloblasts, Auer sticks in the form of beams in leukemic promyelocytes, monocytoid form of nuclei in monoblasts. With the help of cytochemical methods in myeloblasts, enzymes specific for cells of the granulocyte series are detected: myeloperoxidase (MPO) and ASD-chloroacetate esterase;
For myeloid cells, including blasts, the presence of a PAS-positive substance in a diffuse form is characteristic. At the same time, in lymphoblasts, as in all lymphoid cells, the PAS-positive substance is deposited in the form of granules. The absence of signs of myeloid differentiation and the presence of PAS-positive substance in the form of granules, characteristic of lymphocytes, give reason to isolate acute lymphoblastic leukemia.
All variants of ONLL (acute non-lymphoblastic leukemia) were designated by the abbreviation M and the corresponding number (MO — M7), all ALL (acute lymphoblastic leukemia) – by the letter L (Л1 — ЛЗ). The proposed criteria are recognized by most hematologists, including in our country, however, in some cases, the variant of acute leukemia remained undifferentiable.
The use of the achievements of ultrastructural studies, immunology and molecular biology further allowed us to supplement and clarify the classification of FAB. Using electron microscopic studies, a special subtype of leukemic promyelocytes with fine grit not detected by light microscopy, as well as leukemic megakaryoblasts containing specific platelet peroxidase were characterized.
Since the 1980s, the immunophenotypic method has been used to diagnose acute leukemia. The use of monoclonal antibodies (ICA) Cases of acute leukemia with an unclear line of differentiation (undifferentiated, bilinear or biphenotypic) have been proposed to be divided into an independent category.