I found a lump just under her nipple. It moves around a little and doesn't appear to cause her any pain. She seems to have lost her appetite lately but that is not uncommon for her. She is a fit 10 lbs and still enjoys her quite energetic runs and remains playful. Her last heat was May 2-22, 2012. She has never been bred. Has anyone else encountered this? Is it common for dogs to get these lumps and how long should I wait to see if it goes away before going to our vet? Thanks in advance for your advice and comments.