Nodular vasculitis

Fully developed

Artery in a septum in the subcutaneous fat obscured by a dense mixed-cell infiltrate that consists mostly of neutrophils, but also of lymhocytes, plasma cells, and sometimes histiocytes; a thrombus often occluding the lumen the vessel
Extensive necrosis of adipocytes, i.e., necrosis en masse; foam cells, fat "micocysts," and membranous fat necrosis also present in lobules in the subcutaneous fat
Suppuration present in foci within lobules
Granulomatous inflammation distributed in lobules near foci of fat necrosis and of suppuration
Granulation tissue and fibrosis in patchy array within lobules
Mixed-cell infiltrate made up mostly of neutrophils present around vessels and sometimes in the wall of them in the deep retirulcar dermis
Sparse mixed-cell infiltrate around venules of both plexuses in the reticular dermis
Ulceration common