Google has an option to 'remove url' or 'remove from cache' option - what is the procedure for Yahoo to remove a search result (an outdated page or nonexistent page on your site perhaps) or to delete a cached page?
Do you have control over the domain? Send a "410 Gone" header for the page and it will disappear pretty quickly. You can do that via htaccess: Redirect 410 /page/to/delete.html Redirect 410 /page/to/delete2.html Code (markup):