Differential staining pattern of lysozyme in palisading granulomas: an immunoperoxidase study.

Biopsies from palisading granulomas of granuloma annulare, necrobiosis lipoidica, and rheumatoid nodules were examined for the presence of lysozyme (muramidase). This enzyme was identified in paraffin-embedded tissues using a primary antibody to lysozyme and the peroxidase-antiperoxidase technic. Some inflammatory cells in the infiltrate of granuloma annulare stained abundantly for lysozyme, whereas those of necrobiosis lipoidica and rheumatoid nodule stained minimally and negatively, respectively. This pattern of staining may be of diagnostic value and suggests that the histiocytoid cells constituting the infiltrate of granuloma annulare are in some way different from the similar-appearing cells of necrobiosis lipoidica and rheumatoid nodule.