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1. What is lymphoma?
Lymphomas are cancer that arises in lymphocytes. Lymphocytes are WBCs present in lymph nodes, thymus, spleen, bone marrow and specific lymphoid pockets all over the body. They are immune system cells that have varied functions right from fighting and preventing infections to the healing of infections and in autoimmunity. Lymphomas are of 2 types, viz. Hodgkin and Non-Hodgkin. In lymphomas, lymphocytes change, grow in an uncontrolled and uninhibited fashion, each category affects a different type of lymphoid cell and they show variable responses to therapy.
2. What are the symptoms of lymphoma?
Symptoms of lymphoma are fever, chills, night sweats, unexplained weight loss, loss of appetite, painless swelling of lymph nodes in the neck, armpits or groin region, weakness, fatigue, shortness of breath, chest pain, coughing, swollen abdomen or bloating after small meals and itchy skin.
3. What is leukemia?
Leukemias are cancer of blood-forming cells inside the bone marrow. Blood cells are constituents of blood which includes red blood cells, white blood cells and platelets. Their precursors are present in the marrow in an immature form which undergoes maturation to get released into the blood.
4. Which type of LPD is more common?
Lymphocytes are of two types- B lymphocytes and T lymphocytes. In peripheral blood, 80-90% is T-cells. B lymphocytes constitute only a minority (10-20%) in circulating blood, but B-cell LPDs are more common as compared to their T-cell counterparts.
5. What is flow cytometry?
Flow cytometry is a highly specialized laboratory test done on a cytometer with the help of laser beam and fluorescent dyes or tagged substances (antibodies) to identify the types of cells in the blood, bone marrow or lymph node samples. It can also identify particular components within the cell and count a specific number of cells. Its most common use in medicine is immunophenotyping and diagnosis of leukemia and lymphomas.
6. What are the indications of doing a flow cytometry assay?
Indications of doing flow cytometry in LPDs are as follows:
i. Significant lymphocytosis (>6 *109/L) – high lymphocyte counts
ii. Lymphadenopathy and lymphocytosis
iii. Abnormal lymphoid cell morphology on peripheral blood film or bone marrow
iv. Splenomegaly with or without cytopenias (either or all 3 cell lines are low) where LPDs are a possibility
v. Unexplained cytopenias where LPDs are a possibility
vi. Persistent unexplained erythroderma
vii. Presence of splenomegaly and lymphadenopathy but doing a lymph node biopsy is not possible
7. What does CD stand for?
CD stands for cluster of differentiation which is also known as cluster of designation or classification determinant. The pattern of surface CD antigen expression indicates the degree of maturity. It is a protocol utilized to identify and investigate molecules present on cell surfaces. This subsequently helps in providing targets for immunophenotyping of cells and diagnosis of lymphomas and leukemia.
8. What are the normal functions of CD20?
CD20 is encoded by the MS4A1 gene. It is an activated glycosylated phosphoprotein expressed on the surface of all B-cells and its concentration progressively increasing until maturity but expression gets lost upon differentiation into plasma cells. CD20 delivers early signals for activation of B cells thereby allowing resting B cells to respond to antigens on a later date. It plays an important role in the development and differentiation of B-cells into plasma cells.
9. What are the limitations in the utility of CD20?
Small lymphocytic lymphoma is characterized by loss of CD20 expression. Also, CD19 is more sensitive than CD20 in detecting B cell acute leukemia.
10. What is the panel of testing for B cell LPDs?
When B cell LPDs are suspected, you need testing for CD19, CD20, CD79a, CD22, CD38, CD23, CD5, CD10, FMC7, HLA-DR, kappa and lambda. Mature B-cells express surface CD19, CD79a and usually CD20. Immature B-cells characteristically shows cytoplasmic CD19 with or without surface CD19 and CD79a, but are usually CD20 negative. The gold standard for identifying cells of B-cell lineage is cytoplasmic CD79a expression. Peripheral blood B-cells normally expresses CD22 and FMC7 with surface light chain expression of either kappa or lambda at a ratio of between 2:1 and 3:2.
11. How does this test help in lymphoma treatment?
If malignant cells express CD20, specifically targeted immunotherapy can be given for treatment. Rituximab, the first monoclonal antibody against CD20 molecule, has revolutionized lymphoma therapy. This test measures quantitative depletion of malignant CD20 positive cells after giving monoclonal anti-CD20 therapy.
12. Can I directly ask for this testing if I have any symptoms?
It is always the treating physician’s call. After correlating with other lab parameters, symptoms and clinical findings, the decision of doing CD20 testing is taken based upon suspicion of LPDs.
13. What is the therapeutic role of CD20 testing besides lymphoma treatment?
Anti-CD20 agent, Rituximab is used to treating autoimmune disorders, hemolytic uremic syndrome/thrombotic thrombocytopenic purpura, ABO-incompatible transplantation and IgG4-related diseases. So this test is used to quantitatively assess therapeutic B-cell depletion in autoimmune diseases like rheumatoid arthritis, systemic lupus erythematosus, and membranous glomerulonephritis and prevention or treatment of acute humoral rejection in positive crossmatch renal transplant recipients.
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9111591115
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