Objective: 27 cases of nasal NK/T cell lymphomas were studied for the expression of the cytotoxic-granule-associated protein TIA-1, its immunophenotype, genotype and Epstein-Barr virus infection status.

Methods: Immunohistochemical staining for TIA-1, CD3, CD56, CD45RO, CD8, CD20; polymerase chain reaction (PCR) for TCR gamma chain gene and immunoglobulin JH chain gene rearrangement analysis; in situ hybridization for EBER 1/2 and double staining for TIA-1, CD8 with EBER 1/2. 10 cases of lymphoid hyperplasia were used for comparison.

Results: (1) In the 27 cases of nasal NK/T cell lymphomas, most tumor cells expressed TIA-1, CD3, CD45RO and EBER 1/2; expression of CD56 was found in 26 cases; no CD8 or CD20 were detected in tumors cells of this series of cases. Double labelled staining showed that the TIA-1 positive tumor cells coexpress EBER 1/2. TCR gamma chain gene rearrangement was detected in only 1 of the 27 cases. (2) In the 10 cases of lymphoid hyperplasia of nasal pharynx, a small amount of TIA-1 positive cells were present in 8 cases and their distribution similar to that of CD8+ cells, in 4 of these cases a few EBER 1/2+ cells were detected, the number of CD45RO+ cells and CD20+ cells were similar in all 10 cases. Double labelled staining showed that the EBER 1/2+ cells did not coexpress TIA-1.

Conclusions: A high percentage of these tumor cells express TIA-1 and correlate with that of CD56, CD3 epsilon, CD45RO and EBER1/2 in nasal NK/T cell lymphomas. It is suggested that expression of TIA-1 in this tumor may be related to the tumor origin and may also be responsible for its special biologic behavior.