RT Book, Section A1 Grever, Michael R. A1 Lozanski, Gerard A2 Press, Oliver W. A2 Lichtman, Marshall A. A2 Leonard, John P. SR Print(0) ID 1148368032 T1 Hairy Cell Leukemia T2 Williams Hematology Malignant Lymphoid Diseases YR 2017 FD 2017 PB McGraw-Hill Education PP New York, NY SN 9781260117066 LK hemonc.mhmedical.com/content.aspx?aid=1148368032 RD 2024/10/06 AB SUMMARYHairy cell leukemia (HCL) is an uncommon form of adult chronic B-cell leukemia. Whereas the cell of origin is uncertain, at diagnosis the characteristic leukemic cells are found in the marrow, the blood, and the spleen. Patients present with fatigue and infections, and many have splenomegaly. They are often pancytopenic, or may have isolated cytopenias, and usually have monocytopenia. The leukemic cell in classic hairy cell leukemia (HCL-c) has a characteristic immunophenotypic profile (CD11c+, CD19+, CD20+[bright], CD22+, CD25+, CD103+, and CD123+ and CD27−). A variant of hairy cell leukemia (HCL-v), which occurs less frequently, has been identified as a separate entity. A genetic mutation, BRAF V600E, has been identified in the majority of patients with the classic form of this disease but is not present in the variant. This mutation is also present in the hematopoietic stem cells of patients with HCL-c. HCL is characterized by impaired marrow function and immunity, leading to a high incidence of infectious complications. Both pentostatin and cladribine are effective in achieving durable complete remissions. Long-term studies demonstrate prolonged survival of patients, but the disease-free survival curves do not plateau, suggesting that the disease is not cured but subject to relapse. Survival has been markedly improved with the introduction of purine nucleoside analogues and is estimated to be 90 percent at 5-year followup. When patients relapse, high-quality remissions can be achieved with salvage therapy.