. 2019 Jul 17;121(4):344–350. doi: 10.1038/s41416-019-0525-3
© The Author(s), under exclusive licence to Cancer Research UK 2019
This work is published under the standard license to publish agreement. After 12 months the work will become freely available and the license terms will switch to a Creative Commons Attribution 4.0 International (CC BY 4.0).