Cyst-like bump -- what is it?!

Sandie just developed this bump, it's about the size of a grape...it feels kinda like a cyst or something, and it's right in the area where her girth goes on her left side.

If I press on it she doesn't pay any attention, so I know it's not sore or anything, but anyone know what it might be?? It just appeared out of nowhere the other day!

Spider bite, most likely. My horses get them every so often. If it worries you, ask the vet.

It is probably just like what you said a cyst. Our quarter horse mare developed one when she was younger, on her shoulder however and she experiences no pain. We can get it cut out, but there seems to be no need. But seeing as its where her girth is you may want to get the vet to check it out (if you ride her).

I would get it checked out as well if it started to get bigger or something happened to it.

Hope That Helps!