Myelodysplastic syndrome

Significant changes have been made in the classification of myelodysplastic syndromes compared with the FAB classification. Cases with the number of power cells of more than 20%, previously designated as RAIB-T (refractory anemia with an excess of blast at the stage of transformation into acute leukemia), are now considered as acute leukemia, which should be considered completely fair, given the further development of the disease in cases of with so many blast cells and, as a rule, the rapid emergence of all signs of acute leukemia.

It is fair to recognize the release of refractory cytopenia with dysplasia of two or more sprouts of hemopoiesis {refractory cytopenia with multilinear dysplasia). Hematologists are well aware that there are various variants of cytopenia with dysplasia or cases of multilinear dysplasia, but without anemia. Previously, they all had to be designated as refractory anemia.

The allocation of unclassifiable myelodysplastic syndrome is correct, since it is often in the group of myelodysplastic syndromes that there are often cases when, in the presence of obvious features of myelodysplasia, the disease for a very long time is difficult to attribute to a specific variant. A completely new is the allocation of myelo-dysplastic syndrome with an isolated deletion of the long arm of chromosome 5 – 5q- syndrome. In recent years, this syndrome has been considered as a special variant of myelodysplastic syndrome, characterized by significant anemia and at the same time a favorable long course. It is a more favorable prognosis than with other variants of myelodysplastic syndromes, and the absence of the need for intensive therapy serve as the basis for highlighting this option in a separate rubric.

In the rubric of acute myeloid leukemia, the WHO classification has made significant changes compared to the FAB classification, but it should be immediately emphasized that the FAB classification has also been preserved.

According to the WHO classification, all acute myeloid leukemias are divided into 5 categories based on the biological properties of the tumor: 1) with recurring chromosomal abnormalities; 2) with multilinear dysplasia; 3) acute leukemia and myelodysplastic syndromes, the development of which is associated with previous therapy; 4) acute leukemia, which cannot be characterized on the basis of any biological features; 5) acute leukemia of unclear linear affiliation (undifferentiated, bilinear and biphenotypic).

Acute leukemias with recurring chromosomal abnormalities are acute myeloblastic leukemia with t (8; 21), acute myeloid leukemia with eosinophilia in the bone marrow and aberrations of chromosome 16, acute promyelocytic leukemia with t (15; 17) and acute myeloid leukemia with aberrara leukemia with aberara leukemia with aberara leukemia with ab (15; 17) chromosomes 11-11q23.

All leukemias of this group are distinguished by certain biological features: often the characteristic morphology of tumor cells, which allows a diagnosis to be made on the basis of a morphological study and, in most cases, a predictable reaction to modern therapy. Isolation of this group of leukemias is important because they have certain approaches to therapy.
Translocation (15; 17) is pathognomonic for acute promyelocytic leukemia, in which the use of ATRA is necessary from the first days of treatment. This drug has fundamentally changed the prognosis of the disease. With modern therapy, the prognosis for leukemias with t (8; 21) and aberrations of chromosome 16 with eosinophilia in the bone marrow is generally favorable, but for leukemia with aberrations of chromosome 16, only with consolidation of remission with high doses of cytosar. The prognosis is much worse in the presence of changes in the llq23 region, therefore the detection of this aberration necessarily implies intensive therapy.

Thus, the biological characteristics of the leukemias of this group, as well as a specific reaction to therapy, justify the isolation of the leukemias of this group into a separate heading in the classification. At the same time, when establishing a diagnosis for a specific patient, each of the leukemias of this rubric is still characterized in accordance with the FAB classification.