[Histology of cutaneous vasculitides].

Identification of vasculitis by skin biopsy represents the diagnostic gold standard. Skin biopsies should be taken from fresh lesions or from margin of an ulceration and should contain all layers of the skin including subcutis. Classification of vasculitis is based on histological criteria considering the size of the predominantly affected vessel, the distribution of vasculitis in the dermis and subcutis, and the predominant inflammatory cell-type. In cutaneous vasculitis, small and medium-sized vessels of the arterial and/or venous system are predominant affected. Vasculitis of the larger-sized blood vessels is based on inflammatory cells within the wall of the vessel; in small vessel vasculitis, additional features include fibrin within the vessel wall and/or an intraluminal thrombus and/or perivascular and interstitial infiltrates of neutrophils, nuclear dust and extravasated erythrocytes are required for the diagnosis of vasculitis. Leukocytoclastic vasculitis is the most common form of cutaneous vasculitis. An correct diagnosis requires careful correlation of medical history, the clinical, serological, imaging and direct immunofluorescence data, and histologic findings.