Arteritis (vasculitis) is an inflammation of the blood vessels. The inflammation can be localized to a few vessels or it may be systemic. There are seven separate systemic inflammatory disorders of the blood vessels. Each has its own tissue distribution and histological features. However, all of them have in common the perivascular inflammatory response seen with this particular vessel.
Notice the small clear lumen seen centrally in the center of the screen. This lumen is surrounded by a cuff of leukocytes ( the blue cells) about 10 layers thick.