Macroscopic and histological appearance of EBV-induced tumors. (A) Typical appearance of intra-abdominal tumors in one NOD-SCID mouse at autopsy. Tumors were large (0.5-1.0 cm) and solid and contained necrotic foci on cross-section. (B) Histological appearance of tumors in NOD-SCID mice. On light microscopy, tumors were high-grade large-cell lymphomas with high mitotic rates, with varying degrees of tissue necrosis. (C) Immunohistochemical staining confirmed that all tumors were of B-cell origin (brown color indicates CD20⁺ cells; original magnification ×400). (D-E) Immunohistochemical staining of tumors for LMP-1 marker (brown staining; arrows) of EBV lymphoma in both extranodal (D) and nodal (E) regions. (F) Electron microscopy revealing presence of virus (arrows) within intra-abdominal tumor mass (original magnification ×45 000). (G) Immunofluorescent staining of tumors demonstrated the presence of PDCs (red fluorescence) within the tumor periphery using anti–human BDCA-2 mAbs. Images in panels B-E were taken with a 10×/0.30 NA objective; image in panel G was taken with a 40×/0.75 NA objective.