Case 5.

(A) Lymph node showing frank plasmablastic lymphoma, (B) immunostained for HHV-8 and (C) for κ (left) and λ (right) light chains. The HHV-8–positive lymphoma cells show λ light-chain restriction. (D) Polyacrylamide gel electrophoresis of immunoglobulin heavy-chain gene PCR products. Lane 1: PhiXHinfI molecular weight markers (the marker band immediately below the positive control band is 82bp variant CD). Lane 2: positive control B-cell lymphoma. Lane 3: negative control (no DNA). Lanes 4, 5, and 6: repeat amplifications of DNA showing a reproducible dominant band indicating an expanded clone.