Epstein-Barr virus-positive T- and NK-cell lymphoproliferative disorders: Report from the 2023 SH/EA4HP Lymphoma Workshop.

Objectives: To summarize the conclusions of the 2023 Society for Hematopathology/European Association for Haematopathology workshop regarding Epstein-Barr virus (EBV)-positive T- and natural killer (NK)-cell lymphoproliferative disorders (LPDs).

Methods: There were 38 cases submitted to session 3 of the workshop.

Results: Cases included extranodal NK/T-cell lymphoma (ENKTCL), nasal type (n = 16), EBV+ T- and NK-cell LPDs in children (n = 12), primary nodal EBV+ T- and NK-cell lymphoma (n = 5), and other EBV+ T- and NK-cell LPDs (n = 5). The ENKTCL cases highlighted some unusual features like indolent behavior, small cell morphology, and T-cell phenotype, including cases with CD4 and CD30 expression. The differential diagnosis of ENKTCL was illustrated by 4 cases with other primary cutaneous lymphomas. The difficulty in the diagnosis of systemic chronic active EBV disease, its complications, and the sometimes elusive boundaries among the EBV+ LPDs in children are also discussed. The submitted cases also unveiled cases of EBV+ γδ T-cell leukemia/lymphoma not recognized under current classifications and cases of EBV+ CD8+ cytotoxic lymphomas associated with treatment for B-cell lymphomas. The need to have a low threshold to investigate the presence of EBV is highlighted.

Conclusions: The diagnosis of EBV+ T- and NK-cell LPDs is complex and requires a multiparameter approach incorporating clinical information and morphologic and molecular features.