The palisading granulomatous dermatitides comprise a group of different skin diseases with similar histomorphologic forms of granuloma in the skin. Histopathologically characteristic are areas in the reticular dermis and subcutaneous fat with degenerated bundles of collagen surrounded by histiocytes and multinucleate giant cells aligned in a palisade (necrobiotic granuloma). Within the center of palisaded granulomas, mucin or fibrin can be found. The skin diseases presenting histologically with palisading granuloma are granuloma annulare and necrobiosis lipoidica. Palisading granuloma may also be an expression of systemic disease in rheumatoid nodules and necrobiotic xanthogranuloma. Little is known about the pathogenesis. The clinical presentation of the diseases is variable. Therapy is challenging and may not be satisfying.
Keywords: Degenerated collagen; Histology; Mucin; Necrobiotic granuloma; Palisading granuloma.