Footnotes

• Contributors TT coordinated and wrote the initial manuscript. YS reviewed and revised the manuscript from the paediatric oncologist’s viewpoint. YT selected the radiological images, reviewed and revised the manuscript from a paediatric radiologist’s perspective. TY selected histological images, reviewed and revised the manuscript from a pathologist’s perspective. All authors approved the final manuscript and are accountable for this.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests None declared.

• Provenance and peer review Not commissioned; externally peer reviewed.