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Overview

Pathogenesis

  • Hairy cell leukemia arises from B cells, that are normally involved in the process of human immunoglobulins production.[1]
  • However, the exact B cell maturation stage involved in the development of hairy cell leukemia is still unclear.[2]
  • Hairy cell leukemia may also infiltrate the spleen and liver.
  • Extravascular hemolysis may develop due to splenic sequestration and destruction of circulating red blood cells.
  • Hairy cell leukemia rarely infiltrate the peripheral lymph nodes.
  • Bone marrow failure may develop among hairy cell leukemia patients due to:
  • Malignant cells infiltrateion of the bone marrow
  • Reticulin fibrosis of the bone marrow
  • Dysregulated cytokine production
  • The development of bone marrow failure interferes with the normal production of red blood cells and platelets among hairy cell leukemia patients.
  • Production of cytokines, such as TNF α and IL-2R, provide important stimuli for malignant B cells proliferation in hairy cell leukemia.
  • In approximately 40% of hairy cell leukemia cases, malignant cells co-express multiple colonally related IgG, IgA, and IgM isotypes.[3]

Genetics

  • The most common gene involved in the pathogenesis of hairy cell leukemia is BRAF V600E mutations.[4]
  • The BRAF V600E mutations is present in all patients with hairy cell leukemia (classic).
  • The BRAF V600E mutations is not present in patients with hairy cell leukemia (variant).
  • Other genes involved in the pathogenesis of hairy cell leukemia may include:[4]
  • Under expression of chromosomes 3p24, 3p21, 3q13.3-q22, 4p16, 11q23, 14q22-q24, 15q21-q22, 15q24-q25, and 17q22-q24.
  • Over expression of chromosomes 13q31 and Xq13.3-q21

Associated Conditions

Gross Pathology

Microscopic Pathology

  1. Magrath I. The Lymphoid Neoplasms 3ed. CRC Press; 2010.
  2. What is Hairy Cell Leukemia? Hairy Cell Leukemia Foundation (2015) https://www.hairycellleukemia.org/about-hcl/what-is-hairy-cell-leukemia/ Accessed on October, 19 2015
  3. Tiacci E, Liso A, Piris M, Falini B (2006). "Evolving concepts in the pathogenesis of hairy-cell leukaemia". Nat Rev Cancer. 6 (6): 437–48. doi:10.1038/nrc1888. PMID 16723990.
  4. 4.0 4.1 Hairy cell leukemia. Wikipedia (2015) https://en.wikipedia.org/wiki/Hairy_cell_leukemia#Pathophysiology Accessed on Ocotber, 19 2015