Fig 6.

Microscopic features in the wall of the aneurysm corresponding to the boxed regions in Fig 5B. A, Junction of the arterial wall with the aneurysm, showing mural thrombus adjacent to fresh blood in the ostium of the aneurysm (asterisk). B, High power of the area in the box demonstrates organization of the thrombus by sprouts of capillaries (A and B, hematoxylin-orcein-phloxine-saffron). C, Site of rupture shows frayed tearing of the wall, suggesting dislodgment of any focal mural necrosis by the hemorrhage (Masson trichrome). D, Segment of the wall displays focal attenuation (asterisk) and necrosis with attenuated infiltrates of acute inflammatory cells along the outer meningeal portion of the wall. E, High power of the wall shows focal loss of fibroblasts (asterisk); arrowheads indicate remaining fibroblasts (D and E, HE). F, In other regions of the wall, dissecting microhemorrhage (arrow) is associated with the mural necrosis. G, Micro-hemorrhage associated with mural necrosis seen in high power. (F, Masson trichrome; G, HE).