A suspicious item

I have scheduled a senior wellness checkup for Leo this week, mostly to make sure that his heartworm test comes back negative and to get a few weird things looked at (is that a granuloma? what about the hairy tumor thing on his leg?). I was poking around, and there's a lump - a lymph node - behind his right rear leg. I can feel it - that's bad. Now, he's got all kinds of scabs and hot spots on his back quarter - seriously, it's awful! - so it could just be from the infection/scabs/bites/what have you. I hope.  We shall see.