Sysmex Norge

Do you know which disease fits this month’s case? Then test your knowledge in the quiz below!

Can you explain the general tiredness and weight loss of this man? Aplastic anaemia
Myelodysplastic syndrome: refractory cytopenia with multilineage dysplasia (RCMD)
Hairy cell leukaemia
Kostmann’s syndrome, severe congenital neutropenia

Online version of this month´s case:

The correct answer to December´s quiz is:

Hairy cell leukaemia

Scattergrams and microscopy:

Patient history: a 62-year old male came to see his physician with general complaints.



Interpretation and differential diagnosis:

The answer can be inferred from… 

  • Leukocytopenia: WBC < 3.5 x 109/L
  • A relative increase of mononuclear WBC: MONO% + LYMPH% = 73.1%
  • Pseudo-monocytosis: monocyte population visible in the WDF scattergram but not in the WPC scattergrams
  • Presence of neoplastic lymphocytes: ‘Abn Lympho?’ flag
  • No anaemia: HGB = 139 g/L
  • Normal neutrophil granulation: NEUT-GI = 158.2
  • Neutropenia not severe: NEUT# > 0.2 x 109/L


Case history

A 62-year old man visited his physician because he felt weak and tired. Examination of his upper abdomen revealed an enlarged spleen and a complete blood count was ordered.


Case results

The patient had a leukocytopenia with an absolute increased monocyte count in the WDF channel, while monocytes were not detected in the WPC channel. This is a common finding in hairy cell leukaemia and is due to the misclassification of hairy cells as monocytes in the WDF channel (this channel gives information about the cytoplasm, while the WPC channel gives information about the nucleus). The morphology confirmed the presence of hairy cells.


The following answers are incorrect for the described reasons


Aplastic anaemia

Aplastic anaemia is caused by damaged or decreased numbers of pluripotent haematopoietic stem cells, resulting in reduced haematopoiesis (bone marrow failure). The outcome is a pancytopenia, which is the reduction of all types of blood cells: White blood cells, red blood cells and platelets. The presented patient had a neutropenia and thrombocytopenia but no anaemia, and his monocyte counts were increased (due to the misclassification of hairy cells as monocytes: pseudo-monocytosis). In addition, aplastic anaemia is often associated with a relative lymphocytosis, which was not present in this case, and the abnormal lymphocytes detected by the analyser (‘Abn Lympho?’ flag) pointed to a malignant condition instead.


Myelodysplastic syndrome: refractory cytopenia with multilineage dysplasia (RCMD)

The myelodysplastic syndromes are associated with cytopenias and dysplasia in one or more myeloid lineages. In refractory cytopenia with multilineage dysplasia (RCMD), at least two lineages are affected, as observed in the presented patient (NEUT# < 1.8 x 109/L and PLT < 100 x 109/L). Monocyte counts are always below 1.0 x 109/L in RCMD, as was probably the case in this patient as well because the hairy cells are misclassified as monocytes (pseudo-monocytosis). However, there were no signs of dysplasia here: NEUT-GI was normal and there was no anisocytosis or ‘Fragments?’ flag. An RCMD diagnosis was therefore unlikely.


Kostmann’s syndrome, severe congenital neutropenia

Kostmann’s syndrome, a form of congenital neutropenia, is associated with a severe neutropenia with NEUT# <0.2 x 109/L and patients are therefore prone to severe bacterial infections early in life. The genetic mutations leading congenital neutropenia only affect the neutrophil lineage so this diagnosis would not explain the thrombocytopenia observed here. In addition, the neutrophil counts in the presented patient were higher than those observed in Kostmann’s syndrome.

Underlying disease:

Hairy Cell Leukaemia

The first comprehensive description of hairy cell leukaemia (HCL) was published in 1958 by Bouroncle et al who called the condition ‘leukaemic reticuloendotheliosis’ (1) and described clinical symptoms such as fatigue, weakness, splenomegaly, pancytopenia, as well as inaspirable bone marrow and frequent lethal infections. These clinical features are vague, resembling those of many other diseases and make an early diagnosis difficult. HCL affects men five times more frequently than women and is more common in Caucasians and especially in Ashkenazi Jews.


Although the disorder comprises a mere 2% of all leukaemias, debate concerning its cell of origin has made it the subject of disproportionate study. It is now recognised as a low-grade mature B-cell Non-Hodgkin’s lymphoma (2, 3). The B-lymphocyte origin of HCL was established based on a variety of immunological (4, 5) and gene-rearrangement studies (6, 7). For example, most hairy cells lack IgG and C3 receptors for immune phagocytosis and they express significant amounts of cell surface immunoglobulin, typically monoclonal and usually IgM or IgG. Furthermore, a number of B-cell membrane markers are characteristically positive and present a useful profile (see immuno-phenotype below).


A smear review typically reveals cytoplasmic projections, which can be observed in HCL or another mature B-cell neoplasm found in older adults with splenomegaly: splenic lymphoma with villous lymphocytes (SLVL). Furthermore, three variants of HCL are recognised: classic HCL (HCL-C), variant HCL (HCL-V) (8) and Japanese variant HCL (HCL-J) (9). Accurate recognition of these entities is important since they have different clinical and biological features, particularly regarding the response to α-interferon (α-IFN).


The aetiology of HCL has not been determined but it has been suggested that infection with Epstein-Barr virus or human T-lymphotropic virus 2, or exposure to benzene, organophosphorus insecticides or other solvents may be associated with disease development. An increased incidence of HCL is also associated with exposure to occupational, accidental and therapeutic ionising irradiation (10). A number of familial cases have been described, with family members sharing the same HLA haplotype (11, 12).


The clinical course of HCL is inert and treatment is usually not required until severe pancytopenia occurs. Still, most patients eventually will develop progressive disease. Following splenectomy, a minority of patients experience long lasting improvement without further treatment. In progressive disease, the hairy cells infiltrate the patient's reticuloendothelial system, resulting in bone marrow failure and pancytopenia. Hairy cells also infiltrate the liver and spleen, resulting in organomegaly. The complications arising from pancytopenia and concurrent infection cause significant morbidity and mortality. Indeed, infection is one of the most serious and common complications in HCL because patients are neutropenic and severely monocytopenic so both bacterial and opportunistic infections frequently occur. The frequency of severe infection is directly related to the degree of neutropenia, occurring in 46% of patients with a neutrophil count < 0.5 x 109/L but only in 19% of patients with a neutrophil count > 0.5 x 109/L (13).


Neutropenia and monocytopenia may be due to a defect in the monocyte-macrophage system caused by decreased production of granulocyte-macrophage colony-stimulating factor (14). Anaemia is significant in many patients and results from marrow infiltration by tumour cells and splenic red cell pooling (15). Some patients exhibit true erythroid failure (16). Severe thrombocytopenia and platelet dysfunction occurs in about 40% of patients. Since hairy cells have the propensity to fragment, the latter can be mistaken for platelets resulting in erroneous platelet counts both by manual and automated methods (17).


Diagnostic features 

Peripheral blood: The recognition of typical hairy cells in the peripheral blood is useful for suggesting the diagnosis but it is important to remember that not all hairy cells indicate the presence of HCL, nor do all neoplastic cells in HCL samples have cytoplasmic projections. Typically only small numbers of hairy cells are observed and only sometimes these cells dominate the smear. Difficult cases can be confirmed by using immunophenotypic analysis of the buffy coat cells or by performing electron microscopy on suspected cells.


While HCL-C, HCL-V, HCL-J and SLVL are similar morphologically, histological and ultrastructural differences do exist:


  1. Cytoplasmic projections are common in HCL-C, HCL-V and SLVL, but not in HCL-J
  2. Neoplastic cells in HCL-C have a low nuclear/cytoplasmic (N/C) ratio, a central or eccentric, oval, indented, or occasionally bilobed nucleus, reticular (‘lacy’) chromatin, indistinct nucleoli and ribosomal-lamellar complexes
  3. Neoplastic cells in HCL-V are smaller, have a higher N/C ratio, central, rounded, or indented hyperchromatic nuclei, single prominent nucleolus, intensely basophilic cytoplasm but no ribosomal-lamellar complexes; binucleated cells are common
  4. HCL-J: HCL-J cells have round hyperchromatic nuclei, inconspicuous nucleoli and rarely contain ribosomal-lamellar complexes
  5. SLVL: SLVL cells are smaller than neoplastic cells in HCL-C, possess a higher N/C ratio, more condensed chromatin, distinct nucleoli in 50% of cases and may be spindled



Bone marrow: Bone marrow aspiration is typically either unsuccessful (dry tap) or not useful for diagnosis. However, it is very important for making a diagnosis and shows a diffuse infiltrate of mononuclear cells with abundant clear to lightly eosinophilic cytoplasm on haematoxylin and eosin staining. This causes the individual nuclei to be evenly and widely spaced, imparting a characteristic ‘fried-egg’ appearance. Mast cells are often prominent and lymphocytes and plasma cells may be admixed. Bone marrow reticulin fibres are increased, thus accounting for the high frequency of dry taps in patients with HCL. Touch imprints from the trephine biopsy may be valuable for cytological study and tartrate resistant acid phosphatase staining (18). In cases with minimal involvement, immunostaining with B-cell antibodies such as DBA.44 or L26 (CD20) may be useful (19).


Immunophenotypic analysis: The diagnosis of HCL has traditionally been based on microscopy. Until comparatively recently immunophenotypic analysis of peripheral blood by flow cytometry was not widely recognized as a method for diagnosing HCL, perhaps due to the expectation of low yield of neoplastic cells in patients who are characteristically leukopenic. However a recent study (20) has shown that immunophenotyping of peripheral blood is capable of detecting low levels of circulating malignant cells in HCL, even in leukopenic patients. As such, it can be a very useful, non-invasive tool in the diagnosis of this disorder. HCL cells can be identified immunophenotypically in 92% of cases even when these cells represent < 1% of lymphocytes.


Flow cytometry has proven invaluable in the differential diagnosis of ‘hairy’ lymphocytes since the four contenders HCL-C, HCL-V, HCL-J and SLVL often have different immunophenotypic profiles (21). All resemble mature B-cells in that they consistently express CD19, CD20, CD22, and FMC7 and do not express CD5. However, they differ in expression of CD10, CD11c, CD23, CD24, CD25, CD103, and HCL-associated antigen (HC2, an activation antigen defined by a monoclonal antibody raised against lymphocytes of HCL):


  1. HCL-C is typically CD10-, CD23-, CD25+, sIgM+, κ-restricted or λ-restricted, CD11c++, CD103++, HC2++, and variably expresses CD24
  2. HCL-V is typically CD10-, CD23-, CD24-, CD25-, sIgG+, λ-restricted or less frequently κ-restricted, HC2-, dim CD11c+, and variably expresses CD103
  3. HCL-J is CD10-, CD24-, CD25-, sIgG- or weakly sIgG+, κ+, CD11c++ and variably expresses CD103
  4. SLVL is typically CD24+, CD25-, sIgM+, κ-restricted more frequently than λ-restricted, CD103-, HC2-, and variably expresses CD23, CD10, or CD11c



CD11c was originally raised against hairy cells, and recognises a leukocyte adhesion molecule that is also present on monocytes and macrophages, granulocytes, some activated T-cells and in T-lymphoproliferative disorders. CD11c is expressed strongly in virtually all cases of HCL and only occasionally in B-lymphoproliferative conditions other than HCL. CD25 is the p55 receptor for interleukin 2 and is more specific for HCL than CD11c. However, a minority of cases of HCL are CD25 negative.


Differential diagnosis

Hairy cell leukaemia can be confused with other B-cell malignancies that cause splenomegaly. Included in the differential diagnosis of HCL are splenic lymphoma with villous lymphocytes (SLVL), monocytoid B-cell lymphoma (MBCL) and prolymphocytic leukaemia (PLL). MBCL may demonstrate the ‘fried egg’ pattern similar to that of HCL in tissue sections. However, MBCL usually does not present with splenomegaly, peripheral blood or bone marrow involvement. In addition, MBCL is CD25- and TRAP-. PLL is sometimes included in the differential diagnosis because both peripheral blood and spleen are often involved. The prominent nucleoli of PLL and extremely high leukocyte count usually help to establish the diagnosis of PLL. PLL is CD11c-, CD25- and TRAP- and can therefore be distinguished from HCL.


As a more specific diagnostic test for HCL, the gene expression profile of Annexin A1 has been studied (22). It was found that all 62 cases of HCL expressed Annexin A1. Annexin A1 was not expressed in over 250 samples from patients with HCL-V, CLL, PLL, splenic marginal zone lymphoma, nodal marginal zone lymphoma, follicular lymphoma, mantle cell lymphoma, diffuse large B-cell lymphoma, Burkett lymphoma and myeloma.


  1. Bouroncle BA, Wiseman BK, Doan CA (1958): Leukemic reticuloendotheliosis. Blood 13(7): 609-630
  2. Catovsky D, Pettit JE, Galton DA et al (1974): The B-lymphocyte nature of the hairy cell of leukaemic reticuloendotheliosis. Br J Haematol 26(1): 29-37
  3. Foucar K, Falini B, Catovski D et al (2007): Hairy Cell Leukaemia. In: Swerdlow SH, Campo E, Harris NL, et al (Editors): World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues. 4th Edition. Lyon, France. International Agency for Research on Cancer (IARC) Press: 188-190
  4. Golde DW, Stevens RH, Quan SG et al (1977): Immunoglobulin synthesis in hairy cell leukaemia. Br J Haematol 35(3): 359-365
  5. Hannam-Harris AC, Gordon J, Smith JL (1980): Immunoglobulin synthesis by neoplastic B lymphocytes: free light chain synthesis as a marker of B cell differentiation. J Immunol 125(5): 2177-2181
  6. Meyers FJ, Cardiff RD, Taylor CR et al (1984): Hairy cell leukemia has a B-cell genotype. Hematol Oncol 2(2): 145-150
  7. Cleary ML, Wood GS, Warnke R et al (1984): Immunoglobulin gene rearrangements in hairy cell leukemia. Blood 64(1): 99-104
  8. 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): 547-559
  9. Katayama I, Mochino T, Honma T et al (1984): Hairy cell leukemia: a comparative study of Japanese and non-Japanese patients. Semin Oncol 11 (4 suppl 2): 486-492
  10. Stewart DJ, Keating MJ (1980): Radiation exposure as a possible etiologic factor in hairy cell leukemia (leukemic reticuloendotheliosis). Cancer 46(7): 1577-1580
  11. Wylin RF, Greene MH, Palutke M et al (1982): Hairy cell leukemia in three siblings; an apparent HLA-linked disease. Cancer 49(3): 538-542
  12. Çetiner M, Adigüzel C, Argon D et al (2003): Hairy Cell Leukemia in Father and Son. Med Oncol 20 (4): 375-378
  13. Golomb HM, Catovsky D, Golde DW (1978): Hairy cell leukemia: a clinical review based on 71 cases. Ann Intern Med 89 (5 Pt 1): 677-683
  14. Resnitzky P, Barak Y, Karov Y et al (1982): Hairy cell leukemia: defective production of granulocyte-macrophage colony-stimulating factor by peripheral blood cells. Isr J Med Sci 18(8): 845-848
  15. Lewis SM, Catovsky D, Hows JM et al (1977): Splenic red cell pooling in hairy cell leukaemia. Br J Haematol 35(3): 351-357
  16. Orlandi E, Alessandrino P, Baraldi A et al (1982): Erythropoiesis on hairy cell leukaemia: a true erythroid failure. Scand J Haematol 28(2): 97-102
  17. Stass SA, Holloway ML, Slease RB et al (1977): Spurious platelet counts in hairy cell leukemia. Am J Clin Pathol 68(4): 530-531
  18. Krause JR, Srodes C, Lee RE (1977): Use of the bone marrow imprint in the diagnosis of leukemic reticuloendotheliosis (hairy cell leukemia). Am J Clin Pathol 68(3): 368-371
  19. Hounieu H, Chittal SM, al Saati T et al (1992): Hairy cell leukemia. Diagnosis of bone marrow involvement in paraffin-embedded sections with monoclonal antibody DBA.44. Am J Clin Pathol 98(1): 26-33
  20. Cornfield DB1, Mitchell Nelson DM, Rimsza LM et al (2001): The diagnosis of hairy cell leukemia can be established by flow cytometric analysis of peripheral blood, even in patients with low levels of circulating malignant cells. Am J Hematol. 67(4): 223-226
  21. Wu ML, Kwaan HC, Goolsby CL (2000): Atypical hairy cell leukemia. Arch Pathol Lab Med. 124(11): 1710-1713
  22. Falini B, Tiacci E, Liso A et al (2004): Simple Diagnostic Assay for Hairy Cell Leukaemia by Immunochemical Detection of Annexin A1 (ANXA1). Lancet 363: 1869-1870

Sysmex parameters

Our Glossary

An alphabetical listing of scientific terms

Explore our Glossary

Download our Wallpaper 2015

Growing your knowledge
Visit our Academy
Grow your knowledge
Enjoy our Media Centre
  • All
  • Documents
  • Podcast
  • Images
  • Videos
Company movie
See our collection
See our collection
Grow your knowledge http://
See our collection
See our library of smears
Learn more about our concept
XN-L Series overview http://