Elastic NK-cell lymphoma expressing terminal deoxynucleotidyl transferase with Homer-Wright type pseudorosettes formation

Aims: Rosette-forming malignant lymphoma is very rare. We report a blastic NK-cell lymphoma expressing terminal deoxynucleotidyl transferase (TdT) wit h formation of Homer-Wright type pseudorosettes. Methods and results: An 18-year-old boy presented with an enlarged inguinal lymph node. Histologically, the nodal architecture of the lymph node was d iffusely effaced by small to medium sized monomorphic blastoid lymphoid cel ls which frequently formed Homer-Wright type pseudorosettes. Immunophenotyp ing of the tumour using immunohistochemistry and flow cytometry revealed LC A+, CD4+, CD56+, CD43+, TdT+, CD2-, cCD3-, CD8-, CD7-, CD34- and TIA-1-, DN A analysis revealed no gene rearrangement of TCR beta and gamma genes. In s itu hybridization for EBER 1 & 2 was negative, No azurophilic granules were found in the Wright stain. Complete remission was achieved with six cycles of chemotherapy with the CHOP regimen. The disease recurred in the paranas al sinuses and bone marrow 2 years later. Conclusions: Immunophenotypic and genotypic similarities of the present cas e to those of TdT-negative blastic NK-cell lymphoma suggest that these dise ases might be categorized as one entity irrespective of expression of TdT.