Hairy cell leukemia classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Two variants have been described: Hairy cell leukemia-variant[2], which usually is diagnosed in older men (median age above 70), and a Japanese variant. The non-Japanese variant is more difficult to treat than either 'classic' HCL or the Japanese variant HCL.
Classification
Hairy cell leukemia-variant
Hairy cell leukemia-variant, or HCL-V, is usually described as a prolymphocytic variant of hairy cell leukemia.[1] It was first formally described in 1980 by a paper from the University of Cambridge's Hayhoe lab.[2] About 10% of HCL patients have this variant form of the disease, representing about 60-75 new HCL-V patients each year in the U.S. While classic HCL primarily affects men, HCL-V is somewhat more evenly divided between males and females.[3]
Similar to B-PLL in Chronic Lymphocytic Leukemia, HCL-V is a more aggressive disease which is harder to treat successfully than classic HCL. Many treatment approaches, such as Interferon-alpha, CHOP and common alkylating agents like cyclophosphamide provide very little benefit.[3] Pentostatin and cladribine provide some benefit to many HCL-V patients, but with shorter remissions and lower response rates compared to classic HCL. More than half of patients respond partially to splenectomy.[3]
In terms of B cell development, the prolymphocytes are less developed than lymphocyte cells or plasma cells, but are still more developed than their lymphoblastic precursors.
HCL-V differs from classic HCL principally in these respects:
- High white blood cell counts, sometimes in excess of 100,000 cells per microliter;
- More aggressive course of disease that requires more frequent treatment;
- Cells with an unusually large nucleolus for their size;
- Little excess fibronectin (which is produced by classic hairy cells[4]) to interfere with bone marrow biopsies; and
- Low or no expression of CD25 (also called the Interleukin-2 [IL-2] receptor alpha chain or p55) on cell surfaces.[5]
The lack of CD25, which is part of the receptor for a key immunoregulating hormone, may explain why HCL-V cases are normally resistant to treatment by immune system hormones.[6]
HCL-V, which has a high proportion of hairy cells without a functional p53 tumor suppressor gene, is somewhat more likely to transform into a higher-grade disease, with Daniel Catovsky suggesting a transformation rate of 5% in the U.K., which is similar to the Ricther's transformation rate for SLVL and CLL.[3] Among HCL-V patients, the most aggressive cases normally have the least amount of p53 gene activity.[7] Hairy cells without the p53 gene tend, over time, to displace the less aggressive p53+ hairy cells.
Hairy cell leukemia-Japanese variant
Hairy cell leukemia-Japanese variant or HCL-J. There is also a Japanese variant, which is more easily treated.
References
- ↑ "A variant form of hairy cell leukemia resistant to alpha-interferon: clinical and phenotypic characteristics of 17 patients -- Sainati et al. 76 (1): 157 -- Blood". Retrieved 2007-09-10.
- ↑ Cawley JC, Burns GF, Hayhoe FG (1980). "A chronic lymphoproliferative disorder with distinctive features: a distinct variant of hairy-cell leukaemia". Leuk. Res. 4 (6): 547–59. PMID 7206776.
- ↑ 3.0 3.1 3.2 3.3 Matutes E, Wotherspoon A, Brito-Babapulle V, Catovsky D (2001). "The natural history and clinico-pathological features of the variant form of hairy cell leukemia". Leukemia. 15 (1): 184–6. PMID 11243388.
- ↑ "The bone marrow fibrosis of hairy-cell leukemia is caused by the synthesis and assembly of a fibronectin matrix by the hairy cells -- Burthem and Cawley 83 (2): 497 -- Blood". Retrieved 2007-09-10.
- ↑ "Phenotypic analysis of hairy cell leukemia: "variant" cases express the interleukin-2 receptor beta chain, but not the alpha chain (CD25) -- de Totero et al. 82 (2): 528 -- Blood". Retrieved 2007-09-10.
- ↑ "A variant form of hairy cell leukemia resistant to alpha-interferon: clinical and phenotypic characteristics of 17 patients -- Sainati et al. 76 (1): 157 -- Blood". Retrieved 2007-09-10.
- ↑ Vallianatou K, Brito-Babapulle V, Matutes E, Atkinson S, Catovsky D (1999). "p53 gene deletion and trisomy 12 in hairy cell leukemia and its variant". Leuk. Res. 23 (11): 1041–5. PMID 10576509.