Histopathologic findings of proliferative and chronic neointimal lesions after stent graft placement in arteriovenous grafts.

Stent grafts (SGs) are designed to prevent neointimal ingrowth via their expanded polytetrafluoroethylene lining, but restenosis within the stent lumen has been observed in some cases. Here, we report on intra-SG and distal edge stenoses that developed in three patients after SG placement for arteriovenous graft venous anastomotic stenosis. Histopathologic evaluation of the stenoses revealed fibrotic intimal thickening. The intra-SG lesions showed either α-smooth muscle actin-positive spindle cells or chronic fibrotic tissue with hyalinization, and the analyzed distal edge lesion showed α-SMA-positive and partially desmin-positive cells, suggesting myogenic differentiation. To our knowledge, this is the first report to histopathologically confirm intimal tissue formation within the SG lumen. These findings provide histopathologic insight into the spectrum of SG-associated restenosis and suggest that drug-coated balloons, which target intimal hyperplasia, may have therapeutic potential for both intra-SG and distal edge stenoses.