Palisading Granulomatous Dermatitis

This pattern is characterized by an interstitial infiltrate of histiocytes admixed with other inflammatory cells, principally lymphocytes, and zones of altered collagen (Fig. 8.1). Classically, the inflammatory infiltrate surrounds the zones of altered collagen in a wall-like or fence-like fashion, hence the term “palisading.” The classic entities in this differential diagnosis include granuloma annulare, necrobiosis lipoidica, and rheumatoid nodule.