Aims and background: Lymphoid malignancies expressing CD56 are rare and most occur in the nasal or nasopharyngeal region. They derive from natural killer cells or from a small subset of T cells that have granular cytoplasm containing molecules that mediate cytotoxic activity: TIA-1, granzyme B and perforin. Both types are closely associated with Epstein-Barr virus.
Methods: We report the pathologic, immunophenotypic and molecular findings in 14 cases of nasopharyngeal/nasal type T/NK lymphomas.
Results: Clinically, all patients had localized disease and also had symptoms limited to the nose. The neoplastic cells were frequently pleomorphic, and angiocentric growth was common. Combined immunophenotypic and gene rearrangement analyses demonstrated that most of the cases were true NK cell tumors and were either CD56+ and CD3- or CD56+ and CD3+. Immunohistochemical study showed TIA-1 and granzyme B expression in all cases. By in situ hybridization, most of the cases were associated to Epstein-Barr virus, harboring type 1 virus, and polymerase chain reaction amplification across the 30 bp deletion showed high frequency of latent membrane protein-1-deleted variants.
Conclusions: The nasal type T/NK cell lymphoma shows distinctive clinicopathologic, immunophenotypic and molecular features. These results confirm the important role of Epstein-Barr virus as a local factor in their pathogenesis.