Lymphoma is a form of cancer that affects immune cells called lymphocytes, a type of white blood cell. There are many subtypes of lymphocytes and lymphomas. Diffuse large B-cell lymphomas (DLBCL) develop from B lymphocytes (B-cells) and are the most common subtype of non-Hodgkin lymphoma. About one third of DLBCL extend beyond the lymph nodes (“extranodal DLBCL”), and invade vital organs such as the kidneys, lungs, and brain, with an often-fatal outcome. Our ability to predict which patients will develop extranodal DLBCL is limited, and we also lack disease-specific treatments, partly due to an incomplete understanding of how and when these tumors originate. Interestingly, recent evidence suggests extranodal DLBCL share features with autoimmune disorders — conditions in which lymphocytes abnormally react against organs in our bodies, instead of external foes. In this study, we will investigate the relationship between the origin and progression of these diseases, in an effort to better understand how B-cells transform into cancerous cells, disseminate, and expand. Our work could help identify patients at high risk of developing extranodal DLBCL, and unveil key tumor dependencies to be leveraged as specific therapeutic targets.