Multicentric reticulohistiocytosis. Immunohistological and ultrastructural study: a pathology of dendritic cell lineage.

A case of multicentric reticulohistiocytosis is presented with extensive immunohistochemical study of the infiltrate in both paraffin and cryostat sections. Factor XIIIa dermal dendrocyte marker was demonstrated in the cytoplasm of histiocytes, which has not been reported previously in this disease. In addition, the S100 protein stained positive. This immunophenotyping study suggests a dermal dendrocyte lineage with an unusual expression of S100 protein.