Extramedullary T-Lymphoblastic Blast Crisis in Chronic Myeloid Leukaemia: A Unique Cytologic Diagnosis Confirmed by Flow Cytometry.
Aravind Radhakrishnan, Nabhajit Mallik, Pankaj Malhotra et al.
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Case in brief
A 40-year-old man presented with generalized lymphadenopathy, hepatosplenomegaly, anemia, and marked leukocytosis. Bone marrow examination indicated chronic phase chronic myeloid leukaemia (CML) with confirmed BCR::ABL1 fusion. Fine needle aspiration cytology from a cervical lymph node revealed a population of intermediate-sized blasts, and flow cytometry established a diagnosis of extramedullary T-lymphoblastic blast crisis, highlighting the importance of accurate diagnosis.
What made this case unusual
The case illustrates a rare T-lymphoblastic blast crisis in CML, which is typically myeloid in lineage, emphasizing the atypical lymphoid differentiation.
Diagnostic / clinical pearl
Clinicians should consider extramedullary blast proliferation in CML patients presenting with lymphadenopathy, as it may indicate blast-phase transformation despite normal bone marrow findings.
Why it matters
Recognizing this rare presentation is crucial for timely diagnosis and management, as it can precede overt blast transformation in chronic myeloid leukaemia.