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Lymphoma - B cell neoplasms

B cell lymphoma subtypes

Hairy cell leukemia - Variant type

Reviewer: Nikhil Sangle, M.D., University of Utah and ARUP Laboratories (see Reviewers page)
Revised: 25 February 2012, last major update February 2011
Copyright: (c) 2001-2010, PathologyOutlines.com, Inc.

Definition
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● Uncommon variant of hairy cell leukemia (10% of cases) with more aggressive clinical course

Terminology
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● Also called prolymphocytic variant, atypical hairy cell leukemia
● A Japanese variant also exists (Rinsho Ketsueki 2004;45:405), and may respond better to treatment

Clinical features
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● Resembles classic hairy cell leukemia with the following differences: leukocytosis not leukopenia, cells have prominent nucleoli and blastic/convoluted nuclei; negative staining for CD25, Annexin A1 and TRAP on tumor cells; patients are resistant to conventional chemotherapeutic regimen
● 60-75 new patients each year in US
● Older individuals (mean age 70 years)
● Often men with massive splenomegaly, marked lymphocytosis without infection
● Less marrow fibrosis so more successful marrow aspirates
● No neutropenia, no monocytopenia
● More aggressive than classic type
● May be biologically different from classic hairy cell leukemia (Cancer Treat Rev 2011;37:3)
● Rearrangement of VH4-34 gene is more common in variant than classic disease, and is associated with poorer survival (Blood 2009;114:4687)

Treatment
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● Poor response to initial cladribine
● Shorter durations of response, and typically do not respond again to purine analogues after relapse
● Addition of rituximab or anti-CD22 immunotoxins may be helpful

Case reports
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● CD10+, CD25+, CD103-, with poor response to interferon (Arch Pathol Lab Med 2000;124:1710)
● 77 year old man with polycythemia vera (Arch Pathol Lab Med 2003;127:e209)
● With biclonal paraproteinemia (Arch Pathol Lab Med 1997;121:150)

Micro description
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● Morphologic features are intermediate between hairy cells and prolymphocytes
● Cells are large with abundant basophilic cytoplasm, circumferential stellate projections, round, occasionally bilobed nuclei and prominent nucleoli
● Bone marrow: diffuse interstitial or sinusoidal patterns (Arch Pathol Lab Med 2005;129:395)
● Spleen: expansion of red pulp with no / atrophic white pulp; lymphoid cells in sinusoids

Micro / cytology images
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Various images


Intrasinusoidal pattern

Flow cytometry images
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Various images


B cells express CD103 but not CD25 in hairy cell leukemia variant

Positive stains
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● CD11c (bright by flow), CD19, CD22, FMC7; variable CD103 (60%), TRAP (60%) and DBA-44

Negative stains
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● CD5, CD10, CD23, CD25 (Am J Clin Pathol 2005;123:132), CD123, Annexin A1

Differential diagnosis
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● B cell prolymphocytic leukemia: no cytoplasmic projections
● Splenic marginal zone lymphoma: smaller cells may have short cytoplasmic projections; cells have clumpy chromatin, indistinct nucleoli, different staining pattern, splenic white pulp is infiltrated by tumor (Am J Clin Pathol 2005;123:132)

End of Lymphoma - B cell neoplasms > B cell lymphoma subtypes > Hairy cell leukemia - Variant type

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