Acute leukemia of unclear differentiation line – diagnosis

Acute leukemia of unclear differentiation line – diagnosis

A special group is made up of acute leukemias, in which the cells simultaneously exhibit a myeloid and lymphoid orientation of differentiation. In this case, two subclones of cells can be determined, each of which expresses markers characteristic of a single line. These leukemias are called biclonal. In other cases, the blasts coexpress both myeloid and lymphoid or B-or T-lymphoid antigens. This variant of the disease is called biphenotypic acute leukemia (BAL).

Myeloid differentiation is determined by the presence of peroxidase, esterase and / or expression of myeloid (CD13, CD33 and CD65) antigens in blasts. B-lymphoid differentiation is detected by expression of the antigens CD79a, cytoplasmic CD22, cytoplasmic IgM, CD19, CD10 and CD20. T-lymphoblasts are characterized by reactions with MCA to CD3, TCR, CD2, CD5, CD8.

In order to make a diagnosis of biphenotypic leukemia, it is necessary that a positive result be observed with at least two ICA of the same line. It should be noted that some antigens (T-linear CD7, CDla and B-linear CD24) are often present on myeloid cells and cannot serve as markers of the bifenotype. Due to the difficulties in interpreting the results, it became necessary to unify the diagnosis of hybrid leukemia. According to the BAL system, acute leukemia is considered biphenotypic if the sum of cells with myeloid and lymphoid markers exceeds 120. The presence of mixed differentiation is sometimes found only at the molecular-biological level.

It has been shown that during ONLL, rearrangements of the genes of immunoglobulin chains or T-cell receptor genes can be detected.

Biphenotypic leukemias are characterized by a high frequency of cytogenetic abnormalities. In a third of cases of B-lymphoid / myeloid proliferation, the Philadelphia chromosome is determined by t (9; 22), in separate cases — 1 (4; 11) (q21; q23) and anomalies llq23. In patients with T-lymphoid / myeloid biphenotypic leukemia, complex abnormalities of the karyotype are often found.

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