Hairy cell leukemia – etiopathogenesis, diagnosis and modern therapeutic approach

Abstract

Graphical abstract Highlights • A chronic lymphoproliferative disease with characteristic mature clonal B lymphocytes with hairy protrusions • Associated with impaired activity of the B-rapidly accelerated fibrosarcoma (BRAF) protein • Differential diagnosis of hairy cell leukemia, hairy cell leukemia variant and splenic marginal zone lymphoma allows for the selection of effective pharmacological therapy and for risk stratification • Therapeutic approach includes purine analogues, BRAF kinase inhibitors, and anticancer immunotherapy Hairy cell leukemia (HCL) represents 2% of all leukemia cases, with men aged above 55 years being the most affected. The most common symptoms of this type of leukemia include splenomegaly, monocytopenia, and neutropenia. In the basic blood count examination, leukopenia with monocytopenia and granulocytopenia, as well as aplastic anemia and/or thrombocytopenia occur. The mutation of β-rapidly accelerated fibrosarcoma (BRAF) proto-oncogene, which can be found in nearly 100% of patients, is an important feature of HCL. Immunophenotypic analysis of the HCL cells reveals high expression of B-lineage antigens, including CD19, CD20, and CD22. Additionally, CD11c, CD25, CD103, and CD123 belong to specific markers of HCL. Lactate dehydrogenase activity and β-2-microglobulin concentration are also important in the patient’s assessment. The differential diagnosis between HCL, hairy cell leukemia variant (HCL-V) and splenic marginal zone lymphoma (SMZL) is of first importance. Currently, the main treatment for HCL involves the use of purine analogues, excluding pregnant women, individuals with severe infections, and those with relapsing HCL.