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 |