Presence of Restricted Killer Immunoglobulin-Like Receptor Repertoire and Monoclonal T-Cell Receptor γ Rearrangement as Evidence of Mixed NK/T-Cell Differentiation in a Subset of Sinonasal Lymphomas

Abstract

Most sinonasal lymphomas have a restricted killer immunoglobulin-like receptor (KIR) repertoire without a monoclonal T-cell receptor-γ (TCR-γ) rearrangement, implying an NK lineage. However, the lineage assignment of sinonasal lymphoma with a monoclonal TCR-γ rearrangement is unclear because of its mixed NK/T phenotype. The possibility of a mixed NK/T lineage arises with the discovery of T cells with NK features, such as KIR+ T cells or Vα24+ NKT cells. The former might transform into a T-cell lymphoma with both a monoclonal TCR-γ rearrangement and a restricted KIR repertoire; the latter might give rise to a T-cell lymphoma with a monoclonal Vα24 rearrangement and possibly a restricted KIR repertoire. To identify such mixed-lineage lymphomas, we undertook a survey of 15 consecutive sinonasal lymphomas and found six with both a restricted KIR repertoire and a monoclonal TCR-γ rearrangement, consistent with KIR+ T-cell lymphomas. Among these six cases, four female CD56−/CD44−/CD8−/CD45RO+/CD45RA− cases constituted a distinct group with a better prognosis than the rest of the male cases of sinonasal lymphomas. None of the six cases had a monoclonal Vα24 repertoire, thus excluding a derivation from NKT cells. The predominance of KIR+ T cells that normally function in chronic viral infections over Vα24+ NKT cells that typically recognize glycolipid antigens is consistent with the known association of Epstein-Barr virus infection with sinonasal lymphoma. The demonstration of mixed lineage in a mature lymphoid neoplasm is unusual and echoes the World Health Organization classification that placed NK-cell and T-cell lymphomas in a mixed group.