Erythema induratum

Erythema induratum (nodular vasculitis).
(A) Mostly lobular panniculitis with vasculitis. The vessel type involved by vasculitis is variable and may include centrilobular venules, septal veins, or septal arteries; vasculitis may not be demonstrated in every biopsy or every tissue section.
(B) There is a mixed granulomatous infiltrate replacing the lobules with zones of extravascular necrosis.
(C) The zones of necrosis are associated with cellular debris.