The differential diagnosis includes immunoblastic DLBCL and other lymphoid neoplasms with plasmacytic features such as ALK-positive DLBCL, PEL both classic (body cavity-based) and solid (extracavitary) variants, BL with plasmacytoid differentiation, and plasmablastic plasmacytoma/myeloma (Table 1) [67]. The gene discussed is ALK; the disease is primary effusion lymphoma.