Coexistence of ETV6-RUNX1 and MLL aberration among pediatric acute lymphoblastic leukemia: case reports and a literature review.

Background: It is known that ETV6 - RUNX1 is usually related to favorable prognosis, but MLL aberration has been associated with poor prognosis among pediatric acute lymphoblastic leukemia (ALL). However, the outcome of coexistence of ETV6 - RUNX1 and MLL aberration in pediatric ALL patients is unknown. Herein, we report 4 cases of the coexistence of ETV6 - RUNX1 and MLL -partial tandem duplications ( MLL -PTD) in pediatric ALL patients and show the favorable outcome, which was never reported before.
Case Description: The frequency of coexistence of ETV6 - RUNX1 and MLL aberration at our children's medical center was calculated as 0.98% (4/410). All of them were ETV6 / RUNX1 -positive cases that exhibited MLL -PTD, and the 10-year event-free survival (EFS) and overall survival (OS) were both 75%. With the following keywords of " ETV6 - RUNX1 ", " MLL ", "children" and "acute lymphoblastic leukemia", a literature search of coexistence of ETV6 - RUNX1 and MLL aberration was conducted in the database of PubMed, and 4 articles were retrieved finally, involving 16 cases of children. Among the 16 cases of pediatric ALL, the age ranged from 2 to 7 years old, including 9 males and 7 females and the white blood cell (WBC) count was (2.66-68.6)×10 ⁹ /L. In terms of fusion genes, they all had positive ETV6 / RUNX1 . Among them, MLL deletion was exhibited among 8 ETV6 / RUNX1 -positive patients, and 2 cases of der(21) duplication. MLL allelic deletions were shown among the remaining ETV6 / RUNX1 -positive patients. All patients showed a favorable outcome.
Conclusions: The results of our analysis primarily provide compelling evidence that cases with an MLL -PTD or other types of MLL aberration are in fact a distinct subentry among ETV6 - RUNX1 B-cell ALL (B-ALL).
Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tcr.amegroups.com/article/view/10.21037/tcr-23-142/coif). The authors have no conflicts of interest to declare.
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