How is a diagnosis of acute lymphoblastic leukemia (ALL) confirmed?

Updated: Feb 20, 2020
  • Author: Karen Seiter, MD; Chief Editor: Emmanuel C Besa, MD  more...
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Bone marrow aspiration and biopsy are the definitive diagnostic tests to confirm the diagnosis of leukemia. Immunophenotyping helps to elucidate the subtype.

Aspiration slides should be stained for morphology with either Wright or Giemsa stain. The diagnosis of acute lymphoblastic leukemia (ALL) is made when at least 30% lymphoblasts (French-American-British [FAB] classification) or 20% lymphoblasts (World Health Organization [WHO] classification) are present in the bone marrow and/or peripheral blood.

In addition, slides should be stained with myeloperoxidase (MPO) (or Sudan black) and terminal deoxynucleotidyl transferase (TdT), unless another method is used, such as flow cytometry.

Bone marrow samples should also be sent for flow cytometry and cytogenetics. Approximately 15% of patients with ALL have a t(9;22) translocation (ie, Philadelphia [Ph] chromosome), but other chromosomal abnormalities may also occur, such as t(4;11), t(2;8), and t(8;14). Abnormalities of chromosome number are common in ALL.

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