Immunophenotypic and genotypic characterization of nasal lymphoma with polymorphic reticulosis morphology

Nasal lymphoma with polymorphic reticulosis (PR) morphology is now categorized as T/natural killer (T/NK) cell lymphoma. In this study, immunophenotypes and genotypes of proliferating cells in 21 cases with PR were examined. The patients included 13 men and 8 women ranging in age from 20 to 74 (median 37) years. All patients presented with lesions in the upper respiratory tract, mostly in the nasal cavity. Histological specimens obtained from the primary lesions (19 cases) and metastatic cervical lymph nodes (2 cases) were used for analyses. Histologically, polymorphous proliferation was found in 20 cases, and these were thus diagnosed as PR. A monomorphous pattern was found in the remaining last case. Immunohistochemical analysis revealed that the proliferating cells were CD56 (123C3)+ and/or CD16 (2H7)+, TIA-1+ and frequently stained CD3 epsilon+. Tumor cells were frequently stained positively with monoclonal antibodies (mAbs) for T lymphocytes, but were negative for T-cell receptor (TCR) beta and delta chain expression. In situ hybridization analysis using an Epstein-Barr virus-encoded early RNA 1 (EBER-1) probe revealed positive signals in 13 of the 15 cases examined. Southern blotting analysis for clonality of the Epstein-Barr virus (EBV) genome in 12 positive cases confirmed the presence of monoclonal proliferation in 7 cases. The pattern of TCR gamma chain gene rearrangement was examined by PCR analysis of DNA from tumor tissues by the denaturing gradient gel electrophoresis method. The results demonstrated no clonal rearrangement in any of the 21 cases examined, including 7 cases with proven clonal proliferation of EBV-infected cells, indicating the absence of T-cell clones. Our findings strongly suggested that nasal T-cell lymphoma is in fact a NK cell lymphoma.