Clinical features and prognosis of children with acute leukemias of ambiguous lineage under different diagnostic criteria.

Objectives: To study the clinical features and prognosis of children with acute leukemias of ambiguous lineage (ALAL) under different diagnostic criteria.

Methods: A retrospective analysis was performed on the medical data of 39 children with ALAL who were diagnosed and treated from December 2015 to December 2019. Among the 39 children, 34 received treatment. According to the diagnostic criteria for ALAL by World Health Organization and European Group for the Immunological Characterization of Leukemias, the 39 children were divided into two groups: ALAL group (=28) and myeloid expression group (=11). The clinical features, treatment, and prognosis were compared between the two groups.

Results: The 34 children receiving treatment had a 3-year event-free survival (EFS) rate of 75%±9% and an overall survival rate of 88%±6%. The children treated with acute myeloid leukemia (AML) protocol had a 3-year EFS rate of 33%±27%, those treated with acute lymphoblastic leukemia (ALL) protocol had a 3-year EFS rate of 78%±10%, and those who had no remission after induction with AML protocol and then received ALL protocol had a 3-year EFS rate of 100%±0% (<0.05). The children with negative minimal residual disease (MRD) after induction therapy had a significantly higher 3-year EFS rate than those with positive MRD (96%±4% vs 38%±28%, <0.05). Positive was observed in the myeloid expression group, and positive , positive , and hyperleukocytosis (white blood cell count ≥50×10/L) were observed in the ALAL group. There was no significant difference in the 3-year EFS rate between the myeloid expression and ALAL groups (100%±0% vs 66%±11%, 0.05).

Conclusions: ALL protocol has a better clinical effect than AML protocol in children with ALAL, and positive MRD after induction therapy suggests poor prognosis. Hyperleukocytosis and adverse genetic changes are not observed in children with myeloid expression, and such children tend to have a good prognosis, suggesting that we should be cautious to take it as ALAL in diagnosis and treatment.