Lumps are scary, I know, but most of them turn out to be benign. You are veering straight off into the worst case scenario, as we all would in your place, but chances are that it's not what you fear. I thought lumps were less likely to be the bad kind if they are moveable? It's when they are attached that they are more likely to be something nasty.

Let Luna calm you, she's not worrying. If you get upset, then so will she. Sending positive thoughts and best wishes for the check-up.