S8C11aP1a-1: The patterns in the category of leukocytoclastic angiitis are variable. In this example, the changes are mild; there are loose, interstitial infiltrates of neutrophils with occasional fragments of nuclear debris. Necrosis of vessels and perivascular deposits of fibrin are not a feature. The loose spacing of connective tissue fibers may be evidence of edema, but this was an elderly patient; the loose spacing of connective fibers is, at least in part, a manifestation of dermal atrophy (senile atrophy of dermis). The changes are those of a mild “neutrophilic collagenosis” with extravasation of red blood cells; in the absence of clinical impressions, the pattern could be easily dismissed as “acute dermatitis;” infiltrates of this type might even be seen in the dermis adjacent to an acute folliculitis.

S8C11aP1a-2: Yellow arrows identify neutrophils. Green arrows identify fragments of nuclear debris; there are small collections of nuclear debris. It is something of a stretch to characterize the reaction as a leukocytoclastic angiitis and, in doing so, to rely on criteria that require morphologic evidence of damage to the walls of vessels. Extravasation of red blood cells is indirect evidence of vascular damage. The fragmentation of the nuclei of neutrophils is not a phenomenon seen exclusively in the setting of vasculitis.

S8C11aP1a-3: At this magnification, the patterns are “vasculitic” with perivenular infiltrates in upper portion of the reticular dermis. The keratin layer is not altered (a common finding in the setting of a vasculitis). The papillary dermis is edematous (a common finding in the setting of a vasculitis). The epidermis shows interstitial edema (a finding consistent with a vasculitis). There are interstitial infiltrates of inflammatory cells in the upper portion of the reticular dermis (this also is a routine finding in the setting of a vasculitis).