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SUMMARY We have investigated the occurrence, immunohistochemical profile, ultrastructural features and relationships to lymphocytes of the non-lymphoid accessory cells in the dermal infiltrate of five patients affected by B celt lymphoma with secondary involvement of the skin. Typical nonlymphoid accessory cells were found in all cases. Most of these cells had ultrastructural features which resembled those of the poorly differentiated dendritic reticulum cells described in follicular lymphomas of the lymph nodes. The immunohistochemical findings of DRC-1 +, C3b r+ dendritic cells often arranged in follicular-like structures with neoplastic B cells and only few, scattered OKM1+, OKM5+ mononuclear phagocytes support the hypothesis that the vast majority of the non-lymphoid cells observed in our cases were poorly differentiated dendritic reliculum cells. These results and previously published reports indicate that the organization of the dermal infiltrate of B cell lymphomas tends to reproduce the typical arrangement of the B zone of the lymphoid tissue, although with a lesser degree of differentiation, similar to that observed in lymph node follicular lymphomas.