Primary cutaneous B-cell lymphoma with abundant reactive gamma/delta T-cells within the skin lesion and peripheral blood

T-cell/histiocyte-rich diffuse large B-cell lymphoma is characterized by abundant reactive T-cell and histiocyte infiltration within nodal diffuse large B-cell lymphoma, and only limited cases of primary cutaneous T-cell-rich B-cell lymphoma have been documented. These reactive T-cells usually show a T-helper phenotype. Gamma/delta T-cell is a functionally distinct T-cell lineage, which constitutes on average 5% of all T-cells in the peripheral blood. Herein, we report the first documented case of primary cutaneous malignant B-cell lymphoma with abundant reactive gamma/delta⁺ T-cells within the skin lesion and peripheral blood. An 80-year-old Japanese male presented with a gradually enlarged knee nodule. Histopathological study revealed diffuse infiltration of lymphoid cells in the dermis and subcutis. Proliferation of large-sized atypical lymphoid cells was observed among medium-sized lymphocytes with convoluted nuclei. Immunohistochemically, these large-sized atypical lymphocytes were CD20⁺, and relatively many gamma/delta⁺ cell infiltration was also noted. Flowcytometric analysis revealed deviation of lambda+ cells (lambda/kappa 58) and increase of CD3⁺ gamma/delta⁺ cells (6%). Peripheral blood had CD3⁺ gamma/delta⁺ cells (28.8%). Rearrangement of immunoglobulin heavy chain, but not of T-cell receptor beta and gamma chains, was observed. Accordingly, an ultimate diagnosis of cutaneous B-cell lymphoma with abundant reactive gamma/delta⁺ cells was made. Recent studies have shown reactive gamma/delta⁺ T-cell infiltration and/or elevation in the peripheral blood in patients with various types of carcinoma, and that they play a role in the pathogenesis of some carcinomas. Therefore, additional analysis is needed to clarify the role of reactive gamma/delta⁺ T-cells in malignant lymphoma.