What is the role of flow cytometry in the workup of acute lymphoblastic leukemia (ALL)?

Updated: Jul 17, 2018
  • Author: Karen Seiter, MD; Chief Editor: Emmanuel C Besa, MD  more...
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Answer

Although more than 95% of cases of the L1 or L2 subtype of acute lymphoblastic leukemia (ALL) are positive for terminal deoxynucleotidyl transferase (TdT), TdT is not specific for ALL; TdT is absent in L3 (mature B-cell) ALL. However, TdT helps to distinguish ALL from malignancies of more mature lymphocytes (ie, non-Hodgkin lymphoma [NHL]).

Flow cytometry helps to distinguish B-ALL from T-ALL. A classic phenotype for B-ALL is seen in the diagram below. Flow cytometry can also identify whether patients are eligible for certain therapies, e.g. CD20 (rituximab), and CD22 (inotuzumab). Some patients with ALL have aberrant expression of myeloid markers, such as CD13 or CD33.

Diagnostic workup of a patient with pre–B-cell acute lymphoblastic leukemia. Flow cytometry shows that the cells were positive for CD10, CD19, CD22, CD34, and terminal deoxynucleotidyl transferase.

Diagnostic workup of a patient with pre–B-cell acu Diagnostic workup of a patient with pre–B-cell acute lymphoblastic leukemia. Flow cytometry shows that the cells were positive for CD10, CD19, CD22, CD34, and terminal deoxynucleotidyl transferase.

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