Cutaneous EBV-positive γδ T-cell lymphoma vs. extranodal NK/T-cell lymphoma: a case report and literature review.

Primary cutaneous γδ T-cell lymphoma and extranodal natural killer (NK)/T-cell lymphoma (ENKTL), nasal type are two distinct lymphoma entities in the World Health Organization (WHO) classification. We report the case of an aggressive cutaneous lymphoma of γδ T-cell origin showing overlapping features of both lymphomas. A 78-year-old female presented with confluent erythematous plaques with ulcerations over her right thigh. Microscopically, section of the skin showed a diffuse dermal and subcutaneous lymphocytic infiltration with tumor necrosis and angioinvasion. The medium- to large-sized tumor cells expressed CD3, CD8, cytotoxic molecules and T-cell receptor (TCR)-γ but not CD4, CD20, CD30, CD56 or βF1. In situ hybridization for Epstein-Barr virus-encoded mRNA (EBER) was diffusely positive. Polymerase chain reaction-based clonality assay showed a clonal TCR-γ chain gene rearrangement. The features compatible with γδ T-cell lymphoma include dermal and subcutaneous involvements, cytotoxic phenotype, expression of TCR-γ, as well as an aggressive course. On the other hand, the diffuse EBER positivity, angioinvasion, tumor necrosis and cytotoxic phenotype may also fit in the diagnosis of an ENKTL of T-cell lineage. We review the literature on EBER-positive γδ T-cell lymphoma and discuss the diagnostic dilemma using the current WHO classification system.