1Centre for Medical Image Computing, University College London, London, United Kingdom, 2Department of Computer Science, University College London, London, United Kingdom, 3Centre for Medical Imaging, University College London, London, United Kingdom, 4Department of Histopathology, University College London Hospitals NHS Foundation Trust (UCLH), University College London, London, United Kingdom, 5Department of Research Pathology, UCL Cancer Institute, University College London, London, United Kingdom