Plasmacytoid monocytes in Jessner's lymphocytic infiltration of the skin

Plasmacytoid monocytes are normal cell constituents of the human lymph node and have been found to form perivascular clusters in a case of lymphocytic infiltration of the skin. This study was undertaken to analyze the occurrence of plasmacytoid monocyte clusters in biopsy specimens from 54 patients with lymphocytic infiltration of the skin using light microscopy and immunohistochemistry. Variably sized clusters of plasmacytoid monocytes were observed in close association with dermal venules in 16 of 54 biopsy specimens and were composed of medium-sized cells, admixed with pyknotic cells and, occasionally, with tangible body macrophages. Immunohistochemistry on paraffin and on frozen sections facilitated the recognition of plasmacytoid monocytes and showed an immunophenotype similar to that observed previously on reactive lymph nodes. It is concluded that, in analogy with reactive lymph nodes, plasmacytoid monocytes represent a common constituent of the skin-associated lymphoid tissue. The striking perivascular distribution and the immunophenotypical characteristics of these monocyte-derived cells suggest they may have a role in the process of lymphocyte recruitment into the skin.