Is it just dark color or is it a lump or a bump under the skin or does the skin itself feel different (just what you wanted to do - feel your boys testicle). If it's any of those things I would be concerned and consult the vet. If it's just skin discoloration I probably wouldn't be too worried, SuzyQ has spots all over her belly and underneath of varying sizes and colors. But it doesn't hurt to have it checked. I think I'd be concerned that his other testicle hasn't dropped yet. I've never had this problem with any of our male dogs in the past, but I seem to remember that by his age they should both be dropped. Some vets think that dogs with undescended testicles are more prone to certain kinds of cancer - so either way I'd let the vet check it out, if for nothing else your peace of mind.
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