Blastic 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) with 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 diffusely effaced by small to medium sized monomorphic blastoid lymphoid cells which frequently formed Homer-Wright type pseudorosettes. Immunophenotyping of the tumour using immunohistochemistry and flow cytometry revealed LCA+, CD4+, CD56+, CD43+, TdT+, CD2-, cCD3-, CD8-, CD7-, CD34- and TIA-1-. DNA analysis revealed no gene rearrangement of TCR β and γ genes. In situ hybridization for EBER 1 and 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 paranasal sinuses and bone marrow 2 years later. Conclusions: Immunophenotypic and genotypic similarities of the present case to those of TdT-negative blastic NK-cell lymphoma suggest that these diseases might be categorized as one entity irrespective of expression of TdT.