No abstract

SUMMARY:Most sinonasal lymphomas have a restricted killer immunoglobulin-like receptor (KIR) repertoire without a monoclonal T-cell receptor-␥ (TCR-␥) rearrangement, implying an NK lineage. However, the lineage assignment of sinonasal lymphoma with a monoclonal TCR-␥ 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 ϩ T cells or V␣24 ϩ NKT cells. The former might transform into a T-cell lymphoma with both a monoclonal TCR-␥ rearrangement and a restricted KIR repertoire; the latter might give rise to a T-cell lymphoma with a monoclonal V␣24 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-␥ rearrangement, consistent with KIR ϩ T-cell lymphomas. Among these six cases, four female CD56Ϫ 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 V␣24 repertoire, thus excluding a derivation from NKT cells. The predominance of KIR ϩ T cells that normally function in chronic viral infections over V␣24 ϩ 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. (Lab Invest 2003, 83:55-64).