Peripheral T-cell lymphoma with EBV-infected “anaplastic” B-cell proliferation confined to sinuses

An 82-year-old man presented with cervical and axillar lymphadenopathy without symptoms. Cervical lymph node biopsy showed a vague nodular structure (panel A: original magnification ×20 [inset ×200], hematoxylin and eosin [H&E] stain; and panel B: original magnification ×20, immunohistochemistry for immunoglobulin D) with aggregation of atypical lymphoid cells with clear cytoplasm expressing CD3 (panel C: original magnification ×200), CD10, BCL6, and PD-1 (panel C inset: original magnification ×200). Sinuses were partially occupied by large lymphoid cells with anaplastic morphology (panel D: original magnification ×200 [inset ×400], H&E stain). The cells were positive for CD20, CD79a, PAX5, CD30 (panel E: original magnification ×100), Epstein-Barr virus (EBV) LMP1, and EBV-encoded small nuclear early region in situ hybridization (panel F: original magnification ×100) and negative for pan–T-cell markers, CD15, and ALK. Clonality assessment showed monoclonal T cells and polyclonal B cells. A diagnosis of follicular T-cell lymphoma was made.

EBV⁺ B cells, sometimes recognized in peripheral T-cell lymphoma (PTCL), are usually admixed with neoplastic T cells. This suggests abnormal local immune status induced by lymphoma cells. In this case, virtually all EBV-infected B cells were confined to the sinuses. This distribution pattern, mimicking anaplastic large-cell lymphoma, expands the spectrum of B-cell proliferation observed in PTCL. The precise mechanism of the “intrasinusal expansion pattern” is as-yet unknown, but some adhesion molecules of endothelial cells and lymphoma cells may contribute as discussed in intravascular lymphoma. Detailed phenotypic analysis including EBV leads to accurate understanding of pathogenesis.