CD34-TdT-B-ALL masquerading as Burkitt lymphoma

A 23-year-old female presented with widespread petechiae and oral mucosal bleeding. There was no palpable lymphadenopathy or hepatosplenomegaly. Complete blood count included haemoglobin 77 g/L (normal 115–155), white cell count 20.4 × 10⁹/L (4.0–12.0), “blasts” 10.6 (52%), neutrophils 3.3 × 10⁹/L (2.0–8.0), platelets 11 × 10⁹/L (150–400). Peripheral blood morphology demonstrated monomorphic immature mononuclear cells with deeply basophilic cytoplasm and numerous small cytoplasmic vacuoles (Figure 1, left image; 1000x magnification) and markedly elevated serum lactate dehydrogenase (14358 IU; 120–250), suggestive of Burkitt leukaemia/lymphoma. Blood was analysed using standard methods as outlined by the ICSH (International Committee for Standardization in Haematology). Immunophenotyping demonstrated CD10+, CD19+ CD20+, CD22+,CD24+, CD34-, CD38+, CD45+ (dim) and CD58+ with cytoplasmic lambda light chain restriction (without surface light chain expression) consistent with a B-cell lymphoma or pre-B ALL. Bone marrow was markedly hypercellular with 83% neoplastic cells with identical morphology (Figure 1, middle image; 1000x magnification). Immunohistochemistry was negative for TdT and CD34. Chromosomal studies identified an unbalanced t(5;8)(q13;p21) resulting in the loss of part of the long arm of chromosome 5, and deletion of 9p by microarray. Fluorescent in-situ hybridisation did not identify MYC rearrangements typical of Burkitt lymphoma. Targeted molecular studies identified NRAS and BRAF variants and whole genome and transcriptome analysis demonstrated a MEF2D::HNRNPUL1 rearrangement (Figure 1, right image). Prior to molecular results being available, the patient was commenced on R-CODOX-M/R-IVAC, achieving complete remission. With full diagnostic information available, consolidation delivered an ALL regimen. This case highlights how, despite a thorough investigation by all appropriate modalities including morphology, immunophenotyping and cytogenetics, the final correct diagnosis may be delayed until the determination of the molecular profile. Further complicating this case, B-ALL with MEF2D has only recently been described under the category of B-lymphoblastic leukaemia/lymphoma with other defined genetic abnormalities (WHO, 2022).

The authors declare no conflict of interest.

Patient has moved overseas so consent is not feasible. Patient's details are adequately anonymised.

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