Dual Hematologic Malignancies at Presentation: Concurrent T‑Lymphoblastic Lymphoma and Chronic Myeloid Leukemia
Oluwakemi Okwuegbuna,
Nermeen Feltaos
Background: Chronic Myeloid Leukemia (CML) is driven by the BCR::ABL1 fusion and typically
progresses through a chronic phase before evolving into blast phase, most commonly of myeloid or
B-lymphoblastic lineage. T-cell lymphoblastic transformation is exceedingly rare, particularly when
presenting as an isolated extramedullary process at initial diagnosis.
Case Presentation: A middle-aged man presented with marked leukocytosis, anemia, thrombocytopenia,
markedly elevated LDH, massive splenomegaly, and generalized lymphadenopathy. Peripheral blood
smear and bone marrow findings were consistent with CML with a very small population of myeloblasts
and lymphoblasts. This was confirmed by demonstrating BCR::ABL1 fusion using polymerase chain
reaction (PCR). Axillary lymph node core biopsy revealed diffuse infiltration by blastoid T-lineage cells
with expression of CD3, CD7, CD43, CD99, Tdt, and partial CD34, with a high proliferative index. Flow
cytometry of peripheral blood demonstrated an aberrant T-lymphoblastic population comprising 62%
of lymphocytes. FGFR1 rearrangement was not detected by FISH. Overall findings support concurrent
CML with extramedullary T-lymphoblastic transformation.
Discussion: Extramedullary T-cell lymphoblastic crisis is a rare and diagnostically challenging form of
CML progression and may present with minimal or absent marrow involvement. Differentiation from de
novo T-lymphoblastic leukemia/lymphoma requires a high index of suspicion with clinical information,
underscoring the importance of obtaining adequate tissue such as excisional lymph node biopsies,
at presentation. To exclude entities with overlapping clinical and morphologic features, targeted
evaluation for FGFR1 and related kinase fusions is essential, particularly to rule out 8p11 myeloid/
lymphoid neoplasms, which may present with a similar phenotype.
Conclusion: This case represents a highly unusual presentation of synchronous CML and extramedullary
T-lymphoblastic transformation. Comprehensive and adequately triaged sampling is critical to achieve
diagnostic accuracy, guide risk stratification, and inform optimal management in atypical and aggressive
forms of CML progression.
