 If you have an older dog and you can feel a lump on the spleen, first of all, you're a better veterinarian than I am. I can feel a big spleen sometimes, and I can feel it if the thing is a baseball or bigger. But smaller is hard, so it can be something as simple as a lipoma. But if it is a splenic mass, you have to have that addressed because sometimes it's one strike and you're out.