S8C25P11-1: Livedo vasculitis.

S8C25P11-2: Livedo vasculitis is an ischemic disorder of the skin. The effects of the ischemia on the epidermis are variable. In this example, the epidermis on the left is somewhat atrophic. Vessels in the dermis are increased in number; they are arranged in small, lobular aggregates. The vessels are tortuous; they are cut in cross and longitudinal sections. Without regard for the other changes affecting the vessels, the numerical representation of vessels per unit area and the clustering of vessels in lobular arrays qualify the basic patterns as an angiodermatitis (a vasoproliferative process related to stasis, whether clinically evident or not). Without regard for the proliferative changes and the lobular aggregates, fibrinoid necrosis of the walls of vessels (a smudgy eosinophilia) in the absence of significant inflammation qualifies the process as “ livedo vasculitis-like.” This type of vascular necrosis may progress to the formation of a wider area of necrosis (i.e., an infarct). Upon healing, an area of fibrosis and atrophy is produced (atrophie blanche). In the absence of the markers for angiodermatitis, the changes would then qualify as compatible with livedo vasculitis, with the caution that other thrombotic disorders should be considered in the differential diagnosis.

S8C25P11-3: Livedo vasculitis-like changes are represented in this field. Small vessels of the subcutaneous fat are involved; the small vessels show thrombosis with minimal inflammatory infiltrates. A thrombotic disorder should be considered in the differential diagnosis. Small vessels of calcifying panniculitis (calciphylaxis) often show this type of change.

S8C25P11-4:  This section of liver shows a central vessel with a localized area of fibrinoid necrosis of its wall (on the right side of the vessel). The surrounding tissue is partially necrotic. The vascular changes are not diagnostic but, in the appropriate clinical setting, are compatible with thrombotic thrombocytopenic purpura (TTP). The changes are most characteristic when the necrosis focally involves the wall of a small muscular vessel. TTP is a thrombotic disorder.