1. Remember that you can't 100% avoid a cake tumor from forming, but there are ways to help minimize your risk.
2. Work with cakes at room temperature, since that will allow you to put the cakes together and see what they're going to do when they warm up at the party site. Air bubbles are caused when air warms up, expands, and tries to escape from inside of the cake, so give it an opportunity to escape while you're putting the cake together and not later after it's all assembled.
3. Make sure that your fillings are as level as they can get before stacking the layers together. Try to void divots where air can get trapped when you place another layer on top of it.
4. When you put your layers together, kind of roll the layers onto each other to push any air out ahead of the layer, don't just plop them onto each other, which can trap air between the layers.
5. After assembling all of the layers, press gently but firmly on the cake to force out any air that might have been trapped inside the filling layers. You can even put a book or another weighted item on it for a while to force out any air.
6. When the cake is covered with fondant or buttercream, poke a hole or holes in the outer icing to create an "escape valve" of sorts to allow any air out. If you'll be putting flowers on the cake or stacking another tier on top, you can poke holes in the top with a drinking straw.
7. Let the cake sit at room temperature for a while after covering it to allow any air that might want to come out to do so before you start decorating it. It's a lot easier to fix an air bubble when the decorations aren't on the cake yet.
8. After the cake is decorated, refrigerate it so that it will be cold when it's moved to be delivered. This will minimize shifting of tiers and fillings, which can prevent trapped air from squeezing out.
These are just some suggestions that will help avoid cake tumors...If you have any more suggestions please add them in the comments below!
Kara Buntin owns A Cake To Remember LLC, custom wedding cakes in Richmond VA, and cake supplies online at www.acaketoremember.biz and www.acaketoremember.etsy.com