Funding for this research was provided by:
Japan Society for the Promotion of Science (JP17K16572)
Received: 6 September 2019
Accepted: 28 February 2020
First Online: 6 March 2020
Ethics approval and consent to participate
: This study was approved by the ethics committee of Oita University Faculty of Medicine (#1339). The written comprehensive agreement with use of tissue samples for research was obtained from each patient before the operation. The informed consent in this study was obtained by the opt-out method, which the ethics committee approved, because the study contains many former tissue samples.
: Not applicable.
: The authors have no competing interests.