Extramedullary T-lymphoblastic blast crisis in a young male with chronic myeloid leukemia: A rare presentation diagnosed on cytology and flow cytometric immunophenotyping

Background

Extramedullary blast proliferations (EBPs) are known to occur in around 15% of chronic myeloid leukemia (CML) patients in the blast phase. Immunophenotypically, the EBPs are commonly myeloid as compared to the lymphoid. Amongst the lymphoid EBPs, T-lymphoblastic type is considerably rare. Furthermore, the occurrence of EBPs at the initial clinical presentation is extremely rare and such presentations almost always portend the occurrence of an imminent hematological blast crisis shortly.

Case

A 25-year-old male presented with abdominal fullness for 1 month. There was no history of abdominal pain, vomiting, jaundice, weight loss, or night sweats. On clinical examination, the patient was found to have pallor and was febrile. There was hepatosplenomegaly and a single, firm, mobile, left posterior cervical lymph node measuring 1.5 × 1 cm was palpable. Routine blood counts revealed anemia, leukocytosis, and thrombocytopenia. A fine-needle aspiration (FNA) from the cervical revealed T-lymphoid EBP, confirmed by flow cytometry. Subsequently, his bone marrow examination revealed a diagnosis of CML with BCR::ABL1 fusion. Thus, a final diagnosis of CML with extramedullary T-lymphoid blast crisis localized to the cervical lymph node was rendered.

Conclusions

The present report, besides highlighting the utility of FNA cytology in rendering such challenging diagnoses, also reiterates the significance of ancillary techniques, such as flow cytometry, which play a key role in early diagnosis and exact characterization of such rare and aggressive hematolymphoid neoplasms.