IRF4 overexpression is a hallmark of the activated B-cell-like (ABC) type of diffuse large B-cell lymphoma (DLBCL) and multiple myeloma (MM) [3], [13], and is also overexpressed in almost 100% cases of classical Hodgkin lymphoma (cHL), plasma cell myeloma and primary effusion lymphoma (PEL) [16]. Here, IRF4 is linked to primary effusion lymphoma.