This study is an International, multicenter, observational, retrospective trial on patients affected by PBL. The information collected aim to obtain data from the real-life diagnosis, staging, management and treatment and outcome of PBL patients. A centralized pathological review of pathological samples is planned to define the rate of accurate diagnosis and to define a recommended immunohistochemical diagnostic panel for PBL. In addition, exploratory analysis will be performed to better characterize PBL.
