Epstein-Barr virus is present in neoplastic cytotoxic T cells in extranodal, and predominantly in B cells in nodal T non-Hodgkin lymphomas.

Epstein-Barr virus (EBV)-positive T non-Hodgkin lymphomas (T-NHLs) have been described, but it is at present unknown how EBV infects T lymphocytes. It has been postulated that cytotoxic T cells (CTLs) or natural killer (NK) cells can be infected by EBV during the killing of an EBV-infected target cell. The objective of this study was therefore to determine whether the neoplastic cells in EBV-positive T-NHLs (n=221) of various locations have a cytotoxic phenotype. To identify EBV-harbouring cells, combinations were used of EBV-encoded RNA (EBER) in situ hybridization (RISH) and immunohistochemistry for T- and B-cell markers and the cytotoxic proteins TIA-1 and granzyme B. EBV was detected in the neoplastic cells of all nasal T-NHLs (n=9), 5/34 gastrointestinal (GI) T-NHLs, and 2/6 lung T-NHLs, but not in primary cutaneous T-NHLs (n=103). Moreover, EBV was found in the neoplastic cells of 2/48 nodal anaplastic large cell lymphomas (ALCLs), but not in neoplastic T cells of other nodal T-NHLs. However, 5/17 nodal peripheral T-NHLs not otherwise specified (PTCLs NOS) and 1/4 T-prolymphocytic leukaemias did contain EBV-positive non-T cells. Double staining revealed that in EBV-positive extranodal T-NHLs (n=16), the EBER-positive cells had a cytotoxic phenotype (TIA-1- and/or granzyme B-positive). In nodal non-ALCL T-NHLs, the EBER-positive cells were not positive for TIA-1 or granzyme B, nor did they express CD3, CD21 or HECA452. Instead, most of these cells expressed the B-cell marker CD20. These PTCLs NOS with EBER-positive cells showed features of AILD-like T-NHL. It is concluded that neoplastic cells of EBV-positive extranodal T-NHLs always have a cytotoxic phenotype, supporting the view that EBV can infect CTLs. In nodal non-ALCL T-NHL, EBV is only found in T-NHL with AILD-like features and is present in B cells, where it may contribute to the outgrowth of a malignant B-cell clone.