Unifying Concepts

Diagnostic Criteria of Atypical Chronic Myeloid Leukemia (aCML)

Atypical chronic myelogenous leukemia (aCML), BCR/ABL1 negative is a rare disorder classified into the category of myelodysplastic/myeloproliferative neoplasms (MDS/MPN), according to the 2016 revision of the World Health Organization (WHO) classification of myeloid neoplasms and acute leukemia. It is, by definition, a BCR-ABL1-negative clonal disorder sharing myelodysplastic and myeloproliferative features.

Diagnostic Criteria of Atypical Chronic Myeloid Leukemia (aCML)

Feature WHO 2016
Ph chromosome Absent
BCR/ABL1 Absent
Leukocytosis Persistent (≥13×109/L)
Basophil count <2%
Monocyte count <10% of leukocytes
Multilineage dysplasia Dyserythropoiesis and dysmegakaryopoiesis may be present
Dysgranulopoiesis Present
Immature granulocytes ≥ 10% leukocytes
Blasts <20% (blood and bone marrow)
Bone marrow cellularity Hypercellular bone marrow
Other molecular characteristics No rearrangements of PDGFRA, PDGFRB, FGFR1, and PCM1-JAK2
Emphasis on molecular changes (ETNK1, SETBP1)
Other factors WHO criteria for other MPNs not met

FAB, French-American-British; WHO, World Health Organization; Ph, Philadelphia; MPN, myeloproliferative neoplasm; MPN, myeloproliferative neoplasm.



  1. Diamantopoulos PT, Viniou NA. Atypical Chronic Myelogenous Leukemia, BCR-ABL1 Negative: Diagnostic Criteria and Treatment Approaches. Front Oncol. 2021 Nov 17;11:722507. [Medline]
  2. Belkhair J, Raissi A, Elyahyaoui H, Ameur MA, Chakour M. Atypical chronic myeloid leukemia BCR-ABL 1 negative: A case report and literature review. Leuk Res Rep. 2019 May 25;12:100172. [Medline]


Created Jun 24, 2022.

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