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B-Lymphoid Blast Phase of Chronic Myeloid Leukemia

A Case Report and Review of the Literature

Ware, Alisha D. MD*; Wake, Laura MD*; Brown, Patrick MD; Webster, Jonathan A. MD; Smith, B. Douglas MD; Duffield, Amy S. MD, PhD*

doi: 10.1097/PCR.0000000000000332
Case Reviews
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Chronic myeloid leukemia (CML) is a clonal hematopoietic stem cell disorder characterized by a reciprocal translocation, t(9;22)(q34.1;q11.2). This leads to fusion of the BCR and ABL1 genes, encoding an active tyrosine kinase that causes unregulated proliferation of the myeloid lineage. The BCR/ABL1 fusion protein is found not only in CML, but also in a subset of de novo B-lymphoblastic leukemia (B-LL). However, the fusion protein in CML is characteristically the slightly longer p210 variant, whereas the p190 variant is more frequently found in B-LL. Without treatment, CML will progress to accelerated and/or blast phase (BP). Disease progression is often characterized by accumulation of additional chromosomal abnormalities. The development of tyrosine kinase inhibitor (TKI) therapy that targets BCR/ABL1 has revolutionized treatment of CML and vastly improved outcomes, although the disease can still progress despite TKI therapy. Blast phase most commonly manifests as myeloid BP; however, up to 30% of BP presents as lymphoid BP (LBP), typically of the B-cell lineage. The B-lymphoblasts of LBP have a phenotype indistinguishable from that of de novo B-LL. However, LBP typically carries the p210 BCR/ABL transcript and may show distinct chromosomal anomalies, including loss of chromosome 9p. The prognosis for CML-BP is poor, although survival has improved with TKI therapy and stem cell transplant, and LBP has been associated with superior survival compared with myeloid BP. Here we present a case of CML in B-lymphoid BP and review the current literature.

From the Departments of *Pathology

Oncology, Johns Hopkins University, Baltimore, MD.

Reprints: Amy S. Duffield, MD, PhD, 401 N Broadway, Pathology, Weinberg Bldg, Suite 2242, Baltimore, MD 21231. E-mail: aduffie1@jhmi.edu.

This work was supported in part by the Sidney Kimmel Comprehensive Cancer Center grant from the National Institutes of Health (P30 CA006973; J.A.W., B.D.S., A.S.D.).

The authors have no conflicts to declare.

© 2019 Lippincott Williams & Wilkins, Inc.