Determining the type of blast cells in acute leukemia
The study of α-naphthyl acetaserase plays a major role in the diagnosis of monoblasts M5a and M5b. This enzyme is found in most hematopoietic cells, but its isoform, inhibited by sodium fluoride, is characteristic only of cells of the monocyte-macrophage line. In determining non-specific esterase, various substrates are used with equal success: a-naphthyl acetate, butyrate, AS-chloroacetate, etc. Their diagnostic value is close.
The activity of the enzyme in monoblasts without maturation and with maturation, as a rule, is equally high. At the same time, using a panel of various substrates for nonspecific esterase, it is possible to carry out a presumptive differential diagnosis of monoblast and megacaryoblastic leukemias before immunophenotyping.
The result of the PAS reaction has a certain diagnostic value, since a characteristic of most myeloid blasts is the diffuse arrangement of the PAS-positive material in contrast to the lymphoblasts, which are characterized by the arrangement of the reaction product in the form of granules. The results of this study help to distinguish between MO ONLL and ALL. In some cases, in myeloblasts of type MO and erythroblasts, the PAS-positive substance may be in the form of granules.
Different types of blast cells in acute non-lymphoblastic leukemia (ONLL) differ in the antigenic structure of their membranes. The expression of antigens CD33, CD13 is characteristic of the cells of the granulocyte line, they react with ICA to peroxidase. The monocytic line blasts interact with the ICA for lysozyme. The presence of glycophorin A molecules is characteristic of erythroid cells, and CD41 and CD61 are characteristic of megakaryocytes.
Immunological data do not allow a differential diagnosis of granulocytic line blasts, however, the use of immunophenotyping data is crucial for the diagnosis of M0, M6 and M7 variants, since the morphological and cytochemical indicators of these cells do not allow to establish the type of blasts.