Differential diagnosis of acute lymphoblastic leukemia

The differential diagnosis of acute lymphoblastic leukemia and non-Hodgkin’s lymphomas (NHL) in the blast-type leukemization stage necessitates a detailed immunological study. Those hemoblastosis in which the blasts have the phenotype of early progenitors are designated as ALL / NHL, and the rest – as NHL from peripheral cells. So, when expressing antigens of early B-precursors (CD19, CD20, CD22), TdT enzyme and in the absence of membrane immunoglobulin, B-ALL / NHL is diagnosed, and in the presence of T-precursor phenotype – T-ALL / NHL.

Similar difficulties are encountered in the differential diagnosis of acute non-lymphoblastic leukemia (ONL) and myeloid sarcomas. Currently, myeloid sarcomas in the WHO classification are considered in the section of acute leukemia and can be presented as the first manifestation of the disease with rapid leukemization by the type of acute non-lymphoblastic leukemia (ONLL).

The cellular composition of myelosarcoma can be represented by blasts of various types or by maturing elements of the granulocyte series. Morphocytochemical and immunophenotypic characteristics of blasts, cytogenetic abnormalities are identical to those observed in acute non-lymphoblastic leukemia (ONLL).

In patients with multiple myeloma, plasma cell leukemia may occur. It usually manifests itself as a terminal phase of myeloma, although there are descriptions of cases when it is regarded as an independent disease. The leukemic population in the blood and bone marrow is represented by plasmablasts, as well as protoplasmocytes and plasma cells. All elements of the plasma line are morphocytochemically and immunophenotypically characterized as B cells with clonal expression of immunoglobulins.