Received: 24 May 2018
Accepted: 3 September 2018
First Online: 15 September 2018
Ethics approval and consent to participate
: All patients, including legal parent or guardian of minor patients, gave general consent for the use of their tissue/data in research as authorized by the Institutional Review Board of Sapporo Medical University Hospital (No. 292-3012).
: Not applicable.
: The authors declare that they have no competing interests.
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