Paediatric B-lymphoblastic leukaemia with low peripheral blasts: a potential diagnostic pitfall

Area of Science:

• Hematology
• Pediatric Oncology
• Flow Cytometry

Background:

• B cell acute lymphoblastic leukaemia (B-ALL) infrequently presents with minimal peripheral blood (PB) lymphoblasts.
• This presentation can lead to diagnostic challenges, potentially delaying treatment.

Purpose of the Study:

• To describe the clinicopathological features of pediatric B-ALL patients with low peripheral blood lymphoblasts (<5%).
• To identify characteristics associated with this rare presentation.

Main Methods:

• Retrospective analysis of pediatric B-ALL patients.
• Flow cytometry used to quantify peripheral blood lymphoblasts.
• Comparison of patients with <5% PB lymphoblasts versus those with ≥5%.

Main Results:

• Patients with <5% PB lymphoblasts showed distinct clinical features, including more musculoskeletal symptoms and less lymphadenopathy/hepatosplenomegaly.
• Lower white blood cell counts and higher platelet counts were observed in the low lymphoblast group.
• Favorable cytogenetics (ETV6::RUNX1 or high hyperdiploidy without IKZF1 deletion) and less CNS involvement were associated with low PB lymphoblasts.

Conclusions:

• Aleukemic/low PB lymphoblast B-ALL has unique clinicopathological features that can overlap with non-malignant disorders.
• Timely diagnosis necessitates a high index of clinical suspicion and thorough review of PB flow cytometry data.