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

Why did this patient have a monocytosis and anaemia? Mantle cell lymphoma, under therapy
Folate deficiency
Post-infectious monocytosis
Chronic myelomonocytic leukaemia (CMML)

Online version of this month case:

The correct answer to September´s quiz is:

Mantle cell lymphoma, under therapy

Scattergrams and microscopy

Patient history: a patient with a known disease, undergoing treatment.

Table

Interpretation and differential diagnosis

The answer can be inferred from… 

  • Anaemia: Low HGB, RBC and HCT
  • Sufficient haemoglobin incorporation during erythropoiesis: Normal MCH, MCHC, HYPO-He and RET-He
  • Inadequate erythropoiesis rate: RET#, RET% and IRF not increased
  • Presence of malignant lymphocytes: ‘Abn Lympho?’ flag
  • Absence of inflammatory response: No lymphocytosis, ‘Atypical Lympho?’ flag or antibody-synthesizing lymphocytes (AS-LYMPH% = 0.0)
  • Absence of dysplasia signs: Normal NEUT-GI

 

Case history

A 63-year old male patient suffering from mantle cell lymphoma had undergone chemotherapy and his blood was examined to monitor the effect of the treatment.

 

Case results

A normochromic, macrocytic anaemia was observed but the RBC indices that indicate haemoglobin incorporation during erythropoiesis (MCH, MCHC, MicroR, HYPO-He) were all normal. The RET% value was slightly increased but RET# and IRF were normal while MCV and MacroR were slightly increased, indicating an ineffective response to the anaemia caused by chemotherapy-related cell destruction. The WDF channel showed an abnormal lymphocyte population, which triggered a WPC reflex measurement. An abnormal, decreased W1/W2 ratio in the SSC-FSC scattergram of the WPC channel confirmed the presence of abnormal lymphocytes, generating an ‘Abn Lympho?’ flag. The blood smear showed mantle cell lymphoma cells with very heterogeneous morphology, which could be the cause of the false-high monocyte count from the WDF channel. However, a monocytosis as a side effect of the chemotherapy cannot be excluded.

 

The following answers are incorrect for the described reasons

 

Folate deficiency

The mild anaemia observed in this patient was not the result of poor haemoglobin incorporation during erythropoiesis because MCH, MCHC, HYPO-He and RET-He were all normal. Instead, it appeared to be associated with low RBC and HCT values, indicating either a loss of mature red blood cells or a decreased erythropoietic production rate. Like vitamin B12 deficiency, a shortage of folate (also called vitamin B9) results in impaired DNA synthesis and subsequent reduced cell proliferation. This leads to a macrocytic anaemia and, indeed, MCV was slightly increased here. However, the HYPER-He and MCH values were normal, the production of reticulocytes was not decreased and the immature platelet fraction was normal as well, indicating an unaffected thrombopoiesis rate. Therefore, a folate deficiency could be excluded.

 

Post-infectious monocytosis

The observed absolute monocytosis may be a response to either an infective / inflammatory condition or an underlying haematological malignancy. Reactive monocytosis is often associated with viral infections, or with chronic infections or inflammation. In such cases it would be associated with a significant inflammatory response and would have triggered a concomitant immune reaction. However, reactive signs such as a lymphocytosis, an increase of antibody-synthesizing cells (AS-LYMPH) or an ‘Atypical Lympho?’ flag were not present in this patient, which makes a reactive condition unlikely. The ‘Abn Lympho?’ flag pointed to a malignant condition instead.

 

Chronic myelomonocytic leukaemia (CMML)

CMML is a clonal disorder with myelodysplastic as well as myeloproliferative features. The haematological presentation is heterogeneous ranging from isolated monocytosis to myelodysplasia or from a mixed myelodysplastic / myeloproliferative disorder to a forthright myeloproliferative disorder with leukocytosis and splenomegaly, similar to chronic myeloid leukaemia. The diagnostic criteria for CMML include peripheral blood monocytosis in excess of 1000/µl as observed here, while the total leukocyte count may be increased, normal or decreased. However, the presence of abnormal lymphocytes rather than blasts, the absence of dysplasia signs (NEUT-GI is normal) and the high neutrophil to monocyte ratio (6.6 here but below 5 in CMML) made a CMML unlikely here.

Underlying disease

Mantle cell lymphoma (1)

Mantle cell lymphoma (MCL) is an aggressive mature B cell non-Hodgkin lymphoma, characterised by the presence of small to medium-sized CD5-positive B-cells with irregular nuclei. Most patients initially present with lymphadenopathy but the gastrointestinal tract can also be involved. Like some other lymphomas, most MCL cases have the t(11;14)(q13;q32) chromosomal translocation that results in overexpression of cyclin D1. Differential diagnosis from other non-Hodgkin lymphomas such as follicular lymphoma, marginal zone lymphoma and lymphoblastic lymphoma is based on immunophenotyping and immunohistochemistry. Environmental risk factors for MCL are not known but genetics probably plays an important role: In the United States, whites are at a higher risk than African-Americans and men are affected three times as frequently as women.

 

Classification of lymphoid tumours

Lymphomas are diverse, biologically complex neoplasms of the immune system and comprise approximately 4% of new cancers. Historically, several lymphoma classification schemes have been developed based exclusively on morphologic features but this limited approach has proved unreliable and immunophenotyping, by flow cytometry and/or immunohistochemistry, has emerged as a valuable addition to morphologic diagnosis. By combining light scatter characteristics, patterns of antigen expression and DNA content, flow cytometry provides information that is useful for making a diagnosis and subsequently assessing a prognosis.

 

Lymphocytes (2)

To fully understand the pathophysiology of lymphomas, understanding of normal lymphocyte morphology and activity is necessary.

 

Morphological classification

Small lymphocytes: these cells are 7-10µm in diameter with a uniform, round, intensely stained, condensed nucleus and only a thin rim of agranular cytoplasm containing a few ribosomes and organelles. In healthy individuals, the great majority of small lymphocytes are resting in the G0 phase of the cell cycle.

Large granular lymphocytes: these cells, which comprise 5-10% of total peripheral leucocytes, are approximately 20µm in diameter and possess granular cytoplasm.

 

Immunological classification

Lymphocytes are subdivided into three types: B-lymphocytes (B-cells), T-lymphocytes (T-cells) and natural killer (NK) cells. Small lymphocytes are divided immunologically into two major categories: T-cells (60-70%) and B-cells (10-30%). T-cells and B-cells derive from a common precursor and there are no morphological differences between these two cell types but they have differing ontogenies and are functionally distinct. Activated T-cells perform a range of functions, predominantly cytokine production and cellular cytotoxicity, while B-cells produce antibodies.

 

T-cells: lymphocytes that mature in the thymus are called T-cells. They are subdivided into CD4-positive T-cells, also called helper T-cells or Th cells, and CD8-positive cells, which are cytotoxic T-cells. Activated Th cells serve three main functions mediated by cytokines:

Assist B-cell activation (Th2 cells secreting IL-4 and IL-5)

Activate CD8-positive cytotoxic T-cells (Th1 cells secreting IL-2 and IFN-gamma)

Induce delayed type hypersensitivity (Th1 cells secreting IL-2 and IFN-gamma)

Activated cytotoxic T-cells induce cell death by inserting the pore-forming protein perforin into the cell membrane of the recipient cell, most commonly in virus-infected, tumour and allograft cells. Some CD8-positive T-cells suppress certain cell functions and are called suppressor cells. CD4-positive cells amount to approximately 65% of peripheral T-cells and CD8-positive cells to about 35%.

 

B-cells: B-cells do not require the thymus for maturation and exist in germinal centers of the lymph nodes, in the spleen, in the bone marrow and in mucosa-associated lymphoid tissue. They differentiate from pre-pre-B-cells to pre-B-cells and then to B-cells. After stimulation by an appropriate antigen, B-cells undergo clonal expansion and mature into immunoglobulin-secreting plasma cells. After an infection some of the plasma cells persist as memory cells, which can rapidly respond to a recurring infection by the same pathogen. B-cells possess characteristic cell surface markers that can be used for their identification by flow cytometry with fluorochrome-labelled antibodies. Approximately 30% of peripheral lymphocytes are B-cells.

 

Natural Killer (NK) cells: these cells are sometimes called large granular lymphocytes (LGL). NK cells are cytotoxic lymphocytes, distinct from B-cells and T-cells, which participate in both innate immunity and adaptive immunity. They lack the classic cell surface markers of other lymphocytes except CD2 and CD16 and do not have rearranged T-cell receptor or immunoglobulin genes. For this reason they are often referred to as null, non-T- or non-B-cells. NK cells express CD56, which is shared by few other cells and can therefore be used to detect them. Their principal characteristics are nonspecific cytotoxicity, which is activated by cytokines, particularly interferons and IL-2. NK cells are designed to eliminate malignant cells and virus-infected cells by:

Eradicating cells to which antibodies have bound via a process called antibody-dependent cellular cytotoxicity

Destroying cells that lack MHC-I molecules on their surface

 

Classification of lymphomas (3, 4, 5)

The classification of the World Health Organisation (WHO; 3), which is based on the Revised European-American Classification of Lymphoid Neoplasms (REAL; 4) recognises four major categories of lymphoid malignancy based on morphology and cell lineage:

 

  1. Precursor lymphoid neoplasms
  2. Mature B-cell neoplasms
  3. Mature T-cell and NK-cell neoplasms
  4. Hodgkin lymphoma

 

Lymphomas as well as lymphoid leukaemias are included in this classification because solid and circulating phases are present in many lymphoid neoplasms and any distinction between them is artificial. Major differences between the WHO classification and the REAL classification are reviewed by Cogliatti and Schmid (6).

 

Within the precursor lymphoid neoplasm group, two subdivisions are recognised (3):

 

  1. B lymphoblastic leukaemias/lymphomas
  2. T lymphoblastic leukaemias/lymphomas

 

 

Within the mature B-cell neoplasm group, more than 25 subdivisions are recognised (3), such as:

 

  1. B-cell chronic lymphocytic leukaemia/small lymphocytic lymphoma
  2. B-cell prolymphocytic leukaemia
  3. Lymphoplasmacytic lymphoma
  4. Mantle cell lymphoma
  5. Follicular lymphoma (grade 1, grade 2, grade 3a, grade 3b)
  6. Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma)
  7. Nodal marginal zone lymphoma
  8. Splenic B-cell marginal zone lymphoma
  9. Hairy cell leukaemia
  10. Plasma cell myeloma
  11. Diffuse large B-cell lymphoma
  12. Primary mediastinal (thymic) large B-cell lymphoma
  13. Intravascular large B-cell lymphoma
  14. Primary effusion lymphoma
  15. Burkitt lymphoma

 

 

The mature T-cell and NK-cell neoplasms are also subdivided and the conditions include:

 

  1. T-cell prolymphocytic leukaemia
  2. T-cell large granular lymphocytic leukaemia
  3. Aggressive NK-cell leukaemia
  4. Mycosis fungoides
  5. Sezary syndrome
  6. Peripheral T-cell lymphoma, not otherwise characterised
  7. Hepatosplenic T-cell lymphoma
  8. Subcutaneous panniculitis-like T-cell lymphoma
  9. Angioimmunoblastic T-cell lymphoma
  10. Extranodal T-/NK-cell lymphoma, nasal type
  11. Enteropathy-associated T-cell lymphoma
  12. Adult T-cell leukaemia/lymphoma
  13. Anaplastic large cell lymphoma, ALK positive/negative

 

 

Hodgkin lymphoma is subdivided into:

 

  1. Nodular lymphocyte-predominant Hodgkin lymphoma
  2. Classical Hodgkin lymphoma:

 

a)    Nodular sclerosis Hodgkin lymphoma

b)    Lymphocyte-rich classical Hodgkin lymphoma

c)    Mixed cellularity Hodgkin lymphoma

d)    Lymphocyte depletion Hodgkin lymphoma

Literature

  1. Schwerdlow SH, Campo E, Seto M et al (2007): Mantle Cell Lymphoma. 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: 229-232
  2.  Shinton NK (2007): CRC Desk Reference for Hematology, second edition.
  3.  Jaffe ES, Harris NL, Stein H et al (2007): Introduction and Overview of the Classification of Lymphoid Neoplasms. 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: 157-166
  4.  Harris NL, Jaffe ES, Stein H et al (1994): A Revised European-American Classification of Lymphoid Neoplasms: a proposal from the International Lymphoma Study Group. Blood 84(5): 1361-1392
  5.  The Non-Hodgkin’s Lymphoma Classification Project (1997): A clinical evaluation of the International Lymphoma Study Group classification of Non-Hodgkin’s Lymphoma. Blood 89(11): 3909-3918
  6.  Cogliatti SB, Schmid U (2002): Who is WHO and what was REAL? Swiss Med Wkly 132(43-44): 607-617

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