Chronic Myeloid Neoplasms
MDS / MPN
Atypical chronic myeloid leukemia (aCML)

Author: Nikhil Sangle, M.D. (see Authors page)

Revised: 9 March 2017, last major update August 2011

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PubMed Search: Atypical chronic myeloid leukemia [tilte] (aCML)

Cite this page: Atypical chronic myeloid leukemia (aCML). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/myeloproliferativeatypicalCML.html. Accessed June 22nd, 2017.
Definition / general
  • Resembles CML due to increased white blood cell count, primarily neutrophils, > 10% neutrophilic precursors, < 10% monocytes, splenomegaly common (German National Cancer Institute)
  • Differs from CML due to lack of BCR-ABL by cytogenetics or RT-PCR, presence of marked granulocytic and multilineage dysplasia; anemia and thrombocytopenia are common, basophilia is uncommon
  • Median age – 7th / 8th decade; male:female 1:1
  • Median survival less than 2 years, may progress to bone marrow failure or AML; poor prognosis if age > 65 years, female, low platelets, hemoglobin < 10g/dL, WBC count [email protected]; 50 × 109/L (Ann Oncol 2000;11:441)
Diagrams / tables

Images hosted on other servers:

PCM1-JAK2 fusion protein in t(8;9)

Diagnosis
  • WBC count > 13 × 109/L, no BCR-ABL1 gene fusion, no rearrangement of PDGFRA, PDGRB or FGFR1, > 10% neutrophil precursors (promyelocytes, myelocytes, metamyelocytes), basophils < 2% of leucocytes, monocytes < 10% of leucocytes, blasts < 20% of nucleated cells, hypercellular marrow with granulocytic proliferation and dysplasia
Case reports
Microscopic (histologic) description
  • Peripheral blood: usually < 5% blasts; no basophilia / monocytosis; dysgranulopoiesis in the form of pseudo-Pelger-Huët or other nuclear abnormality, abnormal cytoplasmic granularity
  • Bone marrow: hypercellular marrow with increased M/E ratio, marked granulocytic hyperplasia and dysplasia (convoluted lobulation of nuclei, pseudo-Pelger-Huët forms), < 20% blasts
  • Variable dyserythropoiesis and dysmegakaryopoiesis
  • No / minimal basophilia
  • Minimal reticulin fibrosis in some cases
Microscopic (histologic) images

Images hosted on other servers:

Bone marrow smear: various images

Molecular / cytogenetics description
Differential diagnosis
  • CML: BCR-ABL present, prominent basophils, usually no anemia, no thrombocytopenia, no dysplastic granulocytes