He is ginger and white and hasn't been outside except for transport. No other cats, just 2 healthy dogs. No new meds, food or environment. It doesn't seem to be causing him any pain when I've palpated it, nor is he scratching or cleaning it profusely. His appetite and thirst haven't changed at all. We have, however, had an issue with him "acting out" in the past month - eating fabric blinds, scractching on furniture he never had an interest in before, jumping up and knocking things over - generally being a naughty kitty whenever he's left alone, which isn't normal for him. Can't get in to the vet for a few days.