I am assuming that you don't acess to the can.

You should be able to remove the box through the hole. But it won't be an easy task. Then install a ceiling fan box that installs from the room. It uses an expanding bar to thold the box.

However the hole will probably be bigger than the box and either ceiling patching are a large medalion. But some lights might have large enough trimplates.

But there are a number of conversion kits. Google found these.

http://storesense.megawebservers.com/HS1749/Search.bok?category=lights

http://instant-pendant.com/index.asp?page=light

http://www.thecanconverter.com/

Thank you Bill

This is possible to do. There is a kit called "The Can Converter" which will allow you to convert a recessed light either into a pendant. Everything is included in the kit, including a cover plate.

Their website is, www.thecanconverter.com. Where you can order directly from them.

Hope this helps!