ALL vs AML
How to tell ALL and AML apart when a board question makes them look alike.
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Auer rods on peripheral smear or marrow point to AML.
Side by side
Lymphoblast-predominant marrow with TdT positivity and CD10 or CD19 markers favors acute lymphoblastic leukemia.
Myeloblasts with Auer rods and myeloperoxidase positivity favor acute myeloid leukemia.
Clonal proliferation of immature lymphoid precursors replaces normal marrow hematopoiesis.
Clonal expansion of myeloid blasts suppresses normal marrow function and can trigger DIC in APL subtype.
Bone marrow with at least 20 percent lymphoblasts and immunophenotype TdT positive with B-cell or T-cell markers confirms ALL.
Bone marrow with at least 20 percent myeloblasts, MPO positivity, and possible t(15;17) in APL supports AML subtype diagnosis.
The trap
Delaying all-trans retinoic acid in suspected APL while waiting full cytogenetics can allow fatal coagulopathy. If blasts with Auer rods and DIC profile are present, start ATRA immediately.
The repair move
Next best step: obtain urgent hematology consultation, start tumor lysis prophylaxis with aggressive IV hydration and allopurinol, and if APL is suspected begin all-trans retinoic acid immediately while awaiting confirmatory cytogenetics. Broad AML or ALL induction then follows subtype confirmation.
Try a free question
CoreA 50-year-old with pancytopenia has blasts containing Auer rods and fibrinogen 110 mg/dL. What is the next best step in management?
Show answer and explanation
Answer: A. Begin all-trans retinoic acid immediately. Suspected APL is a hematologic emergency and ATRA should begin immediately to reduce early hemorrhagic death.
Why the other choices are tempting
- B. Wrong. Delaying treatment increases mortality from coagulopathy.
- C. Wrong. Iron therapy does not treat acute leukemia.
- D. Wrong. Inpatient urgent management is required.
- E. Wrong. Beta-blockers are unrelated to leukemia treatment.
Flashcards
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Which smear finding rapidly distinguishes AML from ALL?
Auer rods are characteristic of AML.
Which immunophenotype supports ALL?
TdT-positive lymphoblasts with lineage markers such as CD10/CD19 or T-cell markers.
Quick answers
What is the fastest way to tell ALL from AML?
Auer rods on peripheral smear or marrow point to AML.
What is the key clue for ALL?
Lymphoblast-predominant marrow with TdT positivity and CD10 or CD19 markers favors acute lymphoblastic leukemia.
What is the key clue for AML?
Myeloblasts with Auer rods and myeloperoxidase positivity favor acute myeloid leukemia.
What is the common trap with ALL vs AML?
Delaying all-trans retinoic acid in suspected APL while waiting full cytogenetics can allow fatal coagulopathy. If blasts with Auer rods and DIC profile are present, start ATRA immediately.