Bone marrow neoplastic
Bone marrow - neoplastic myeloid
MDS / MPN
Atypical chronic myeloid leukemia
Author: Nikhil Sangle, M.D.
Topic Completed: 1 August 2011
Minor changes: 12 February 2021
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: Atypical chronic myeloid leukemia [title] (aCML)
Table of Contents
Definition / general | Diagrams / tables | Diagnosis | Case reports | Microscopic (histologic) description | Microscopic (histologic) images | Molecular / cytogenetics description | Differential diagnosisCite this page: Sangle N. Atypical chronic myeloid leukemia. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/myeloproliferativeatypicalCML.html. Accessed February 27th, 2021.
Definition / general
- aCML
- 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 &@62; 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
- 83 year old man with leukemic pleural effusion (J Korean Med Sci 2006;21:936)
- 2 year old with t(5;12) successfully treated with imatinib (Leuk Res 2004;28 Suppl 1:S65)
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
- May have t(8;9) (Cancer Res 2005;65:2662)
- No BCR-ABL rearrangement
- Must use RT-PCR because
- fusion gene may be present with normal karyotype (Hematol Oncol. 2006;24:86) and
- karyotype may normalize after imatinib treatment (Leukemia 2004;18:1340)
Differential diagnosis
- CML: BCR-ABL present, prominent basophils, usually no anemia, no thrombocytopenia, no dysplastic granulocytes
