Recent literature suggests that a subgroup of Hairy Cell Leukemia(NCL), sometimes called Variant Hairy Cell Leukemia(HCL-V)l my in fact be a different disease not related to HCL at all and which my respond to rituximab to a much higher extent than common Hairy Cell does. It is thought that this variant is what used to be called Leukemic Reticuloendotheliosis in the past. It is an uncommon disorder accounting for approximately 0.4% of chronic lymphoid malignancies and 10% of all HCl cases. In contrast to HCl-C, HCl-V is a more aggressive disease and according to the new WHO classification it is no longer considered to be biologically related to HCl-C. Patients with HCl-V have an elevated white blood count, easy-to-aspirate bone marrow, unlike HCL which is difficult to aspirate, and weak reactivity to tartrate – resistant acid phosphatase (TRAP). Immunophenotypically, HCl-V cells are positive for CD103 and CD11c and negative for CD25. The HCl-V cells express also the B-cell antigens, CD19, CD20 and CD22. The HCl-V patients have frequently an unmutated Ig gene configuration. Currently, the principles of therapy for this rare disease derive from uncontrolled single institutional studies, or even single case reports. In contrast to HCl-C, the HCl-V response to purine nucleoside analogs (PNA) is limited to partial responses in approximately 50% of patients. However, complete responses were observed in patients treated with rituximab and anti-CD22 immunotoxins
Jones G, Parry-Jones N, Wilkins B, Else M, Catovsky D, British Committee for Standards in Haematology. Revised guidelines for the diagnosis and management of hairy cell leukaemia and hairy cell leukaemia variant. Br J Haematol. 2012 Jan;156(2):186-95. [60 references]
Jones G, Parry-Jones N, Wilkins B, et al. Revised guidelines for the diagnosis and management of hairy cell leukaemia and hairy cell leukaemia variant. Br J Haematol 2012; 156:186.
Hagberg H, Lundholm L. Rituximab, a chimaeric anti-CD20 monoclonal antibody, in the treatment of hairy cell leukaemia. Br J Haematol 2001; 115:609.
Robak T. Current treatment options in hairy cell leukemia and hairy cell leukemia variant. Cancer Treat Rev 2006; 32:365.
Arons E, Suntum T, Stetler-Stevenson M, Kreitman RJ. VH4-34+ hairy cell leukemia, a new variant with poor prognosis despite standard therapy. Blood 2009; 114:4687.
Robak T. Hairy-cell leukemia variant: recent view on diagnosis, biology and treatment. Cancer Treat Rev 2011; 37:3.
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