CD34 and abdominal aortic aneurysm: Ryer et al. described a possible proinflammatory role of stem cells in abdominal aortic aneurysms and it was observed in infrarenal aortic wall specimens collected from patients with abdominal arterial aneurysms (AAA) undergoing surgical repair; a significantly great number of c-kit+ and CD34+ cells also express macrophage marker CD68 but not the SMCs marker SM22 or the fibroblast marker FSP1.