Human tissue responses to metal stents implanted in vivo for the palliation of malignant stenoses

Background: We sought to determine the histologic effects of metal stent placement on tumor tissue and on normal tissue proximal and distal to the tumor in patients with expandable metal stents implanted in vivo. Methods: Twelve patients with 10 to 16 mm uncovered Wallstents were studied, 5 with esophageal stents, 4 with biliary stents and 3 with antral-duodenal stents. Stent duration ranged from 18 days to 15 months. Eleven autopsy specimens and one surgical specimen were examined, The organs with the stent in place were removed, and histologic specimens were obtained using a special saw-microtome that cuts through the tissue and the material of the stent. Results: In all organs examined, the stent was incorporated into the material of the tumor to a varying degree. In the normal areas above and below the stenosis, the stent was incorporated into the wall of the organ and was covered by a collagenous reactive layer on the luminal aspect. The collagenous reaction was limited and did not cause exuberant growth or obstruction in any of the cases. Conclusions: The struts of uncovered Wallstents of 10 to 16 mm in diameter migrate into the submucus space above and below the tumor, probably by pressure necrosis, and become incorporated into the wall of the organ.