Ziggy has a lump on the right side of his neck, where it meets his jaw. It's been there for a while, but was very small and the vet didn't seem too worried this summer. But in the past 2 weeks it's been growing, and it's almost tennis ball sized. It's rock hard but he doesn't mind when we touch it/poke it.
Here's a brief history: Ziggy is a 6 year old Mustang that came off the "range" this Spring. He is up to date on his vaccinations and wormings - probably for the first time in his life. His fall vaccinations were given on 10/31. He has spent the past two months at the trainers. There was a filly who came down with pigeon fever, but they had no contact with each other & none of the other horses have shown symptoms. He has no other "sick" symptoms - no fever, runny nose, behavior change, lethargy, etc.
Any ideas? I'm not even sure what to google right now... Thanks in advance! He just came home and seeing it is making the weekend seem like a very long time to wait, even if he is acting normally.