I lurk on this board alot so Hello! sorry to hear about your pooch and I know it is frustrating but you have to think postive. My dobergirl who is 7yrs had a lump on her chest like that and it scared me to death!! It was lypolma (sp?) fatty tumor she has had serveral but never on her chest. Can you move the tumor?? Does it feel attached??? With my experience if they move it is the and does not feel attached it is most likely a fatty tumor and watch to see if it grows, outline it with a piece of paper and pen to see if it grows rapid. If it is a fatty tumor have it removed (when you have the $) and have the vet send it to the University of Mich. for testing. Good luck my fingers are crossed.