Many lumps are simply a nuisance and nothing to worry about. However, there are some that can be quite invasive and cause some significant disfigurement if left to grow unchecked, and there are some that are so malignant that they can spread their cancer to the inside of the body. The best thing to do would be to get your pet to the doctor so that we can evaluate it. We might start by aspirating out a few cells onto a slide, or we might recommend removal right away. Sometimes we tell you it’s nothing to worry about and is just a sign of a little bit of aging.