The back end of the lighter assembly is threaded. There is a stamped metal "nut" that holds it in place. With a pair of small, 90 degree angled pliers, you should be able to grab the edge of the "nut" and pull the top edge towards you. Once it is broken free, you can spin it off easily by hand.
To help you visualize this, the "nut" looks kind of like a miniature bundt cake pan, and you want to grip the outer edge of the pan that would be "up" when the cake is in the oven.
Mmmmm. Cake. Hope this helps.
-Mike