Ph+ T-cell ALL or CML Presenting in T-cell Blast Phase? A Case Report and Diagnostic Challenge

Document Type

Conference Proceeding

Publication Date

4-2026

Publication Title

Pediatric Blood & Cancer

Abstract

Background: Philadelphia (Ph) chromosome, the defining feature of chronic myeloid leukemia (CML), is characterized by the BCR:ABL1 gene translocation resulting in two oncogenic proteins, p190 and p210. CML accounts for 3% of pediatric leukemias with 1%–2% of cases presenting in blast phase. The p210 fusion transcript is classically associated with chronic phase CML. The p190 transcript is commonly found in Ph+ acute lymphoblastic leukemia but is seen in 1%–2% of CML. This can elicit diagnostic challenges in patients presenting with Ph+T-cell ALL, an exceptionally rare diagnosis with only 30 cases reported in the literature. Objectives: Describe a case of Ph+ T-cell ALL with concern for CML in blast phase and highlight minimal residual disease (MRD) discordance between flow cytometry and BCR:ABL real time PCR (RT-PCR).

Design/Method: Single subject case report. Results: A 16-year-old male with 6 weeks of fatigue, URI symptoms and cervical lymphadenopathy, presented with massive splenomegaly, hyperleukocytosis (434K/uL), anemia (hgb 4.9 g/dL), thrombocytopenia (42 K/uL), and 97% peripheral blasts. Peripheral blood flow cytometry was consistent with TALL. FISH testing revealed BCR:ABL/t(9;22) gene fusion in 96.5% of nuclei and deletion of TCRB (7q34) region in 22% of cells. BCR:ABL RT-PCR demonstrated only a minor breakpoint (p190) fusion. He started treatment on AALL 1631 with imatinib for Ph+ T-cell ALL. Due to persistent disease at end of induction 1B with a MRD by flow cytometry of 2.3% and 8.5% by BCR:ABL RT-PCR, he transitioned to T-cell targeted treatment, NECTAR therapy with dasatinib. Following cycle 1 of this therapy, he had persistent MRD discordance, 0.072% by flow cytometry and 0.46% by BCR:ABL RT-PCR. Cell sorting demonstrated BCR:ABL positivity in both CD3 and CD15 cells, suggesting possible CML in T-cell blast phase. Given high-risk disease and persistent MRD, he underwent allogeneic matched sibling peripheral blood stem cell transplant following total body irradiation-based conditioning. His BCR:ABL RT-PCR remained positive for 3 months posttransplant. He continued dasatinib for1-year post-transplant. One year bone marrow exam demonstrated normal morphology with 100% donor chimerism and 18 months post-transplant BCR:ABL RT-PCR remains negative.

Conclusion: Ph+ leukemias are uncommon in the pediatric population and association with T-ALL at any age is exceedingly rare. This case report highlights the diagnostic uncertainty in differentiating CML in blast phase from Ph+ T-ALL.

Volume

73

Issue

Suppl 2

First Page

s168

Comments

American Society of Pediatric Hematology/Oncology (ASPHO) Conference, April 29-May 2, 2026, Minneapolis, MN

Helen DeVos Children’s Hospital

Last Page

s169

DOI

10.1002/1545-5017.70343

ISSN

1545-5009

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