<h4>Background</h4>Double-expressor lymphoma (DEL), defined by concurrent MYC and BCL2 protein overexpression in diffuse large B-cell lymphoma (DLBCL), is associated with poor prognosis, but precise risk quantification and optimal treatments remain unclear.<h4>Methods</h4>We conducted a two-stage evidence synthesis. This evidence concerns the gene BCL2 and lymphoma.