Programmed death 1 (PD-1) and its ligand (PD-L1) as a new frontier in cancer Immunotherapy and challenges for the Pathologist: state of the art.

The interest in better understanding the immune-microenvironment and tumor cells crosstalk, recently leads to focus on immune checkpoints role, notably on PD-1/PD-L1 axis. The current backdrop concerning cancer immunotherapy is constantly evolving and new biomarkers still need to be granted in this dynamic context. This review tries to get lights on PD-L1 complex scenario mainly focusing on troubling issues in assessing this marker in daily practice. It's still necessary to look deeper into this matter in order to make easier the pathologists-oncologist interaction. © Copyright Società Italiana di Anatomia Patologica e Citopatologia Diagnostica, Divisione Italiana della International Academy of Pathology.