Cutaneous polyarteritis nodosa

Different stages of cutaneous vasculitis lesions in polyarteritis nodosa, which are similar to those seen at extracutaneous sites.
(A) Involvement of a single small artery in the subcutis by a necrotizing vasculitis, which is neutrophilic rich at its inception and then evolves into a predominance of mononuclear cells.
(B) Inflammatory infiltrate in the adventitia with marked necrosis and fibrin deposition of the vascular wall.