My 8 yr. old Labrador Retriever was just discovered to have a fist sized lump just below her right rib cage. She is not off her food, doesn't drink an abnormal amount of water, still loves to run and play, stool appears fine. This is not a fatty tumor - this seems to be something internal I just can't figure out what. Our Veterinarian (the one we see for routine care yearly) just left for a 2 week vacation. Safe to wait or not? Any ideas what it might be?