Leukemia Lymphoma Phenotyping

Leukemia Lymphoma Phenotyping

 

During evaluation of peripheral lymphocytosis (absolute lymphocytosis >4,000/µL), the possibility of a malignant disorder requires evaluation.

  • If absolute lymphocytosis is established, causes such as infectious mononucleosis should be considered
  • If lymphoproliferative disorder remains a significant possibility after clinical evaluation, cell surface phenotyping of lymphocytes should be performed
    • Phenotyping of cell surface antigens on peripheral blood lymphocytes usually performed using flow cytometry
      • Technique provides percentage of lymphocytes positive for a particular antigen and density of antigens
      • Normal peripheral blood lymphocytes consist of approximately 10% B-cells, 80% T-cells and 10% NK cells

Most commonly used markers (CD = cluster designation)

  • B-cell – CD10, CD19, CD20, CD22, CD23, CD24, CD79b, CD103, Kappa, Lambda, FMC7, Cytoplasmic Kappa, Cytoplasmic Lambda
  • T-cell – CD1, CD2, CD3, CD4, CD5, CD7, CD8, T-cell receptor (TCR) alpha- beta, TCR gamma-delta, Cytoplasmic CD3
  • Myeloid/Monocyte – CD11b, CD13, CD14 (Mo2), CD14 (MY4), CD15, CD33, CD64, CD117, myeloperoxidase
  • Miscellaneous – CD11c, CD16, CD25, CD30, CD34, CD38, CD41, CD42b, CD45, CD56, CD57, CD61, HLA-DR, glycophorin, TdT, bcl-2

B-cell lymphoproliferative disorder probable if immunoglobulin light chain restriction is demonstrated by surface typing of kappa or lambda

  • B-cell chronic lymphocytic leukemia (CLL) or mantle cell lymphomas are suspected if CD5 is positive and CD10 is negative
  • Circulating mantle cell lymphoma can be mistaken morphologically for B-cell CLL
    • Mantle cell lymphoma considered when
      • CD20, CD19 – strong intensity
      • Surface immunoglobulin – strongly expressed
      • CD23 –  absent
      • Diagnosis
        • Molecular and FISH testing
        • Requires t(11;14) translocation demonstration
      • CLL is more likely when:
        • CD20 – strong intensity
        • Surface immunoglobulins –  weakly expressed
        • CD 23 – present
  • Circulating germinal center cell derived lymphoma is probable if CD10 is positive and CD5 is negative
    • Germinal center lymphomas– follicular, Burkitts, diffuse large B-cell
    • Diagnosis
      • Some cases can be confirmed by the demonstration of the t(14;18) breakpoint by PCR or FISH testing
      • PCR detects approximately 80% of t(14;18) translocations found in follicular lymphoma
        • FISH is more sensitive for this translocation in fixed tissue
      • FISH can also detect a c-MYC or BCL-6 rearrangement for Burkitts or diffuse large B-cell lymphoma
  • Hairy cell leukemia has a characteristic phenotype that is CD5-, CD10-, CD11c+, CD25+ and CD103+
    • CD103 antigen (also known as B-ly7) is present in virtually all cases
    • CD11c and CD25 are less specific, but present in virtually all cases of hairy cell leukemia

T-Cell Lymphoproliferative Disorders

  • Most show abnormalities of pan T-cell antigens CD2, 3, 5, or CD7
  • T-cell disorders
    • Proliferating lymphocytes are usually positive for CD3
    • Most common form is large granular lymphocytosis
    • Usually show rearrangement of T-cell antigen receptor locus
    • Clonality assessed by flow cytometry, PCR or Southern blot
  • Large granular lymphocytosis is suspected if percentage of CD16, CD56 or CD57 positive cells >50%, or if absolute count of these cells >2000/µL
  • Peripheral T-cell lymphoma (NOS)
    • Phenotypic abnormalities
  • NK cells
    • CD3 is absent
    • Occurs in a minority of cases   
  • Angioimmunoblastic lymphoma has characteristic CD10 and CD4 positive and CD52, 56 and 16 negative
  • Anaplastic large cell lymphoma – positive CD30 and ALK(+)
    • Some pan T-cell antigens are frequently deleted
  • Sézary syndrome should be considered if CD7 and CD26 are negative
  • Clinical spectrum and prognosis are variable in both T-cell and NK-cell types
    • Most behave in indolent fashion


Click here for table of Common Hematologic Antigens


See Also