Digital slides as an effective tool for programmed death ligand 1 combined positive score assessment and training: Lessons learned from the "Programmed death ligand 1 key learning program in Head-and-Neck squamous cell carcinoma" - Albino Eccher; Gabriella Fontanini; Nicola Fusco; Ilaria Girolami; Paolo Graziano; Elena Guerini Rocco; Maurizio Martini; Patrizia Morbini; Liron Pantanowitz; Anil Parwani; Anna Maria Pisano; Giancarlo Troncone; et al. (Elsevier, 2021)