The single most commonly used marker to identify B-cell lymphomas is CD20. Certain types of B-lineage lymphomas are characteristically negative for CD20, however. These include plasmablastic lymphoma, HHV8+ primary effusion lymphoma (and its extracavitary or solid variant), B lymphoblastic lymphoma/leukemia and ALK+ diffuse large B-cell lymphoma. On encountering one of these high grade lymphoma...
