Well it really depends on what type of lump it is on how serious it is and the cost of surgery. It sounds like it may be a hernia or some sort because of the coloring but without seeing it its hard to say. I would have your vet check it out and give you an idea of how serious. If its a simple hernia it may only take a short surgery to close the herniated area to prevent further damage. If its a tumor of some sort, depending if there's muscle involvement it could be a major or minor surgery, so as you see, there's a lot depending on it. If he's severly overweight, more than likely, more of what he has are lympomas or fatty tumors that once you get weight off him they should decrease in size. I would have your vet check him out and give you an estimate on what they think it is.
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