ALL L1 presents with lymphoblasts and a hypercellular marrow with >25% lymphoblasts, MPO NEG, Sudan Black NEG, and PAS POS. Which diagnosis is most consistent?

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Multiple Choice

ALL L1 presents with lymphoblasts and a hypercellular marrow with >25% lymphoblasts, MPO NEG, Sudan Black NEG, and PAS POS. Which diagnosis is most consistent?

Lineage determination of blasts hinges on cytochemical staining and the blast phenotype. In this marrow, the blasts do not show myeloid enzyme activity: both myeloperoxidase (MPO) and Sudan Black are negative, which argues against acute myeloid leukemia. The blasts are positive with PAS, a pattern commonly seen in lymphoid blasts. When you have more than 20–25% blasts in the marrow, that defines an acute leukemia rather than a chronic process. Putting these clues together, the blasts are of lymphoid origin, and the morphology fits the L1 subtype, leading to acute lymphoblastic leukemia (ALL) with the L1 appearance. Hairy cell leukemia would typically show hairy cytoplasmic projections and TRAP positivity; CLL would involve mature-appearing lymphocytes rather than blasts; AML would more often be MPO or Sudan Black positive.

Lineage determination of blasts hinges on cytochemical staining and the blast phenotype. In this marrow, the blasts do not show myeloid enzyme activity: both myeloperoxidase (MPO) and Sudan Black are negative, which argues against acute myeloid leukemia. The blasts are positive with PAS, a pattern commonly seen in lymphoid blasts. When you have more than 20–25% blasts in the marrow, that defines an acute leukemia rather than a chronic process. Putting these clues together, the blasts are of lymphoid origin, and the morphology fits the L1 subtype, leading to acute lymphoblastic leukemia (ALL) with the L1 appearance. Hairy cell leukemia would typically show hairy cytoplasmic projections and TRAP positivity; CLL would involve mature-appearing lymphocytes rather than blasts; AML would more often be MPO or Sudan Black positive.

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