B-cell ALL is a subgroup of acute lymphatic leukemia. It is characterized by proliferation and accumulation of malignant degenerated, immature hematopoietic cells, so-called blasts in bone marrow and blood.
It is the most common childhood malignancy with a peak incidence of 2-5 years. Although ALL is primarily a disease of the bone marrow and blood, all other lymphoid (e.g., lymph nodes, spleen) and non-lymphoid organs (e.g. liver, CNS, skin, bone) may also be infested. The leukemic blasts displace physiological leukopoiesis, erythropoiesis, and thrombopoiesis and cause cytopenias of all three cell lines. This is followed by susceptibility to infection, anemia and clotting disorders. Furthermore, flu symptoms, enlarged lymph nodes, hepatosplenomegaly, and bone pain are common.
The pathogenetic causes of ALL remain unclear in most cases. It is known that certain chromosomal changes (for example, trisomy 21), radioactive rays, certain chemicals and drugs may play a role in the development of a leukemia.
With the help of immunophenotyping, two main groups of ALL can be distinguished depending on the precursor cell: the T cell ALL (25% of the cases) and the B cell ALL (75% of the cases ). Depending on the degree of differentiation, B-cell ALL can be classified into pro-B, common, pre-B, and mature B-ALL.
The cells are classified according to their degree of ripeness. This means that a pro-B-ALL is an immature form, the common ALL is followed by the pre-B ALL. The mature-cell B-ALL already has many features of mature B lymphocytes, showing a rapid progression and a frequently large tumor mass with an increased incidence of CNS and organ involvement.