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Lymphoma - B cell neoplasms

B cell lymphoma subtypes

Hairy cell leukemia

Reviewer: Nikhil Sangle, M.D., University of Utah and ARUP Laboratories (see Reviewers page)
Revised: 7 February 2012, last major update February 2011
Copyright: (c) 2001-2010, PathologyOutlines.com, Inc.


● Rare chronic leukemia that commonly presents with massive splenomegaly, with tumor cells containing hair-like projections


● Formerly known as leukemic reticuloendotheliosis

Clinical features

● Mean age 52 years, range 20-80 years; 80% men
● Commonly presents with massive splenomegaly with obliteration of white pulp and involvement of red pulp, pancytopenia (50%), marrow fibrosis, monocytopenia, infections in 1/3; frequently atypical mycobacterial infections with weakness and weight loss; minimal lymphadenopathy (eMedicine)
● Bone marrow aspiration biopsies unsuccessful (‘dry tap’) in 30-50% due to marrow fibrosis
● Excellent prognosis, with near normal life expectancy with appropriate treatment
● Many patients who achieve a complete remission by morphologic criteria have minimal residual disease demonstrable by flow cytometry or immunohistochemistry, and may be at higher risk for earlier relapse (Blood 2010;115:21)

Case reports

● 55 year old man with nodular patch in cecum at routine colonoscopy (Case of the Week #95)
● 42 year old man with WBC count of 98K (Arch Pathol Lab Med 2003;127:253)
● With blastic transformation (Arch Pathol Lab Med 1997;121:707)
● With transformation to large cell lymphoma (Hum Pathol 2004;35:1423)


● Unlike other tumors, single agent therapy is common and usually successful (US National Cancer Institute, Wikipedia)
● Purine analogs 2-deoxycoformycin and 2-chlorodeoxyadenosine and interferon cause complete remission in 76-85% and markedly improve disease free survival (Hematol Oncol Clin North Am 2006;20:1153)

Micro description

● Tumor cells are larger than small lymphocytes, modest pale blue agranular cytoplasm with circumferential threadlike extensions seen with phase contrast microscope, round or indented/folded (oval) nuclei, no distinct nucleoli
● Residual follicles often present
● Cells line pseudosinuses
● Blood lakes often present

Bone Marrow:
● Diffuse or focal involvement with irregular, poorly demarcated infiltrates
● Cells may be loosely spaced
● Hairy cell is 10-14 microns with abundant, clear to lightly basophic or eosinophilic cytoplasm with surface circumferential delicate and broad projections
● May have cytoplasmic vacuoles and azurophilic granules
● Oval / folded / indented nuclei with variable chromatin and no prominent nucleoli
● May be perinuclear halo in formalin fixed tissue due to abundant cytoplasm
● Prominent cell borders (‘fried-egg appearance’) with formalin fixation
● Marked marrow fibrosis and increased mast cells are common
● No/rare mitotic figures

Stromal variant: leukemic cells are spindled

Micro images

Bone marrow biopsy - increased reticulin fibrosis

Bone marrow trephine biopsy (figures A-F)

Post-treatment bone marrow with minimal residual disease: H&E and DBA.44+ (figure 1B)

Cecal lesion from above Case of Week: H&E and DBA.44

Fig 1: large lymphocytes with abundant cytoplasm, eccentric nuclei, often cytoplasmic projections; Fig 2-TRAP+; Fig 3-hypercellular bone marrow with monotonous “fried egg” lymphocytes with abundant cytoplasm



Various immunostains: CD20+;   CD25+;   DBA-44+;   TIA1+

Cytology description

● Small/intermediate sized cells with moderate pale-gray cytoplasm, cells have circumferential hair-like and short, blunt cytoplasmic projections, round/oval nuclei with smooth nuclear borders, stippled chromatin, occasional nucleoli (Cytojournal 2006;3:1)

Cytology images

Peripheral blood

Lymph node aspirate

Bone marrow aspirates

Peripheral smear

● Monocytopenia, leukopenia, often no/rare leukemic cells; 5-10% have WBC > 10 billion/L, usually due to tumor cells

Positive stains

● Typical pattern is positive for B cell markers (CD19, CD20, CD79a, PAX5), CD11c, CD25, CD103; negative for CD5, CD10, CD23, but variations are common (Am J Clin Pathol 2006;125:251)
● CD19, CD20, CD22, DBA.44, CD79a, PAX5, TRAP (tartrate resistant acid phosphatase)
● Also CD11c, CD25, CD103 (Am J Clin Pathol 2009;131:586), HC2, FMC7
● Annexin A1 (but also expressed by T-cells and myeloid cells, so compare with CD20 areas)
● Reticulin shows thickened fibers that may circle individual cells and infiltrate normal appearing areas
● TIA1 in 56% (Mod Pathol 2004;17:840)
● CD10 in 10% (Am J Clin Pathol 2003;120:228)
● Flow cytometry with CD11c, CD20, CD25 and CD103 is useful (Arch Pathol Lab Med 2007;131:383))
● Combined TRAP and DBA44 is sensitive and fairly specific (Am J Surg Pathol 2005;29:474)
● Variable staining for cyclin D1/bcl1 (Mod Pathol 2000;13:1308)
● Atypical immunophenotyping in 34% (Am J Clin Pathol 2006;125:251)

Negative stains

● CD5, CD10, CD23, CD79b

Differential diagnosis

Splenic marginal zone lymphoma: nodular involvement of splenic white pulp, not obliteration; cytoplasmic processes are polar, not circumferential; negative for DBA.44, TRAP, CD103, Annexin A1
Nodal marginal zone B cell lymphoma
Mastocytosis: tryptase+, CD117+, Giemsa+, toluidine blue+, negative for B cell markers

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

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