Discordant reaction of Leu4 and rabbit anti-human CD3 epsilon in sinonasal 'T'-cell lymphoma.

Twelve cases of sinonasal 'T'-cell lymphoma were studied immunohistologically with a panel of antibodies that included two antibodies to CD3, Leu4 and rabbit anti-human CD3 epsilon. Leu4 was positive in five cases, whereas rabbit anti-human CD3 epsilon was positive in 11. This discordant reaction of the antibodies, suggestive of cytoplasmic CD3 epsilon +, CD3 delta-, and CD3 gamma-, has recently been demonstrated in activated adult natural killer (NK) cells also. Leu4-negative cases had the phenotype CD2+, CD5-, CD7+/-, T-cell receptor (TCR)-, and NK cell markers+, and had non-rearranged TCR genes. These findings suggest that a large group of sinonasal 'T'-cell lymphomas is derived from NK cells.