PBL should be morphologically distinguished with anaplastic or plasmablastic plasma cell myeloma, immunoblastic cell type diffuse large B-cell lymphoma, anaplastic diffuse large B-cell lymphoma, ALK-positive large B-cell lymphoma, primary effusion lymphoma and HHV8-related origin of Castleman's disease, multi-center B-cell lymphoma, and so on. This evidence concerns the gene ALK and Castleman disease.