tumor on genitalia

Question
Hello,

I do not expect a diagnosis as I am a Pediatrician and know how this is.

I have a 13year old male Border Collie/Lab mix. He is intact by the way.  He's been healthy his entire life except for a right ear hematoma repair back in June of this year.  Recently (maybe 3 weeks ago) he's developed a small maybe l/2 inch very red soft tumor/growth which looks like an "M" on the right side of his penis area on the fur.  He's white down there.  When I palpate it it isn't painful and it feels like it extends about 2cm subcutaneously.  I've had 2 vets look at it and they both agree it's worrisome and recommend biopsy.  What I'd like to know if it's something you've seen before and is it common in that area?  I'm ok with the diagnosis of cancer for he is after all 13.  Is there some type of cancer which likes to show up in this area?  The vet yesterday palpated his belly (as I have) and felt nothing enlarged.  Thankfully he is acting normally and eating well. The proverbial (acting like nothing is wrong)

Thanks ahead of time for anything you can tell me.


Answer
Certainly it could be cancerous but many skin tumors in dogs are not.   

The only tumor that I know of that is particular to the genitals of dogs is transmissible veneral tumor (TVT).   Since he is intact, this could be a possibility if he has had contact with other dogs.  If you do a websearch for TVT you will come up with several websites with more detailed info and pictures that you can compare to your dog's growth.