Histologic and immunohistochemical study of KSHV-positive plasmablasts in lymphoproliferative lesions in case 1.

Plasmablastic lymphomas show confluent sheets of plasmablasts (A, hematoxylin-eosin) that express exclusively λ light chain (B) and high levels of cytoplasmic IgM (C). CD27 (brown), a marker for mature B cells, is expressed in 20% to 30% of KSHV-positive (blue) plasmablasts (D). Double staining shows that vIL-6 (brown) is strongly expressed in 10% to 15% KSHV-positive (blue) plasmablasts (E); hIL6-R (blue) is expressed in most KSHV-positive (brown) cells (F).