TABLE 4.

Histological findings in patients with giant cell arteritis (GCA) (35).

Histological features In GCA
Location	All three arterial layers may be involved. In severe cases there is a diffuse widespread inflammatory infiltration Main inflammatory bulk is located in the adventitia media junction The inflammatory infiltrate has a concentric ring appearance, with the thicker ring adjacent to adventitia-media junction and the thinner ring in proximity to media-intima junction (transmural inflammation) The media is relatively spared The myofibroblastic proliferation of intima leads to occlusion of the lumen
Types of cells	CD-4+ lymphocytes and macrophages are the most commonly seen Giant cells are seen in 50–75% of cases and their absence do not preclude the diagnosis Plasma cells and eosinophils may also be seen; neutrophils are rarely present
Other histological patterns
Periadventitial and adventitial inflammation Isolated intima inflammation	The inflammation in GCA spreads from adventitia to intima. Inflammation affecting only the periadventitial vessels, the vasa vasorum and the adventitial tissue may also be seen Cautious interpretation is needed taking into account clinical, laboratorial and imaging findings Rarely seen
Healed arteritis Atherosclerosis Fibrinoid necrosis	Features of healed inflammation: irregular intima proliferation, changes in the internal elastic lamina, fibrosis and neovascularization of the media and adventitia in the absence of ongoing active inflammation Note that: These changes can also be seen as a result of normal aging (atherosclerosis) Regular intima proliferation with focal loss of the internal elastic lamina. Calcifications could be present Rarely seen (Evaluate for other diagnoses, if clinical findings are not typical for GCA)