How is microscopy of PAN?

• Lesions are segmental. • Characteristically, the lesions at different stages of development coexist in different vessels or even within the same vessel. • Transmural necrotizing inflammation of small to medium-sized arteries → weakens the wall of artery → can lead to aneurysms or rupture. • Gross: Nodular lesions mainly at the points of arterial branchings. Aneurysms may also be seen.