anybody had experience with mast cell tumors under the skin?

Oreo appears to have another mast cell tumor under his skin. The first one a few years ago was like a bb under the skin and could be moved around with your finger like a small cyst. No surface appearance like a sore or anything. The vet aspirated the first one and found lots of mast cells. She removed it and there was no recurrence at the site. This one is about 4 inches away. Both are located just below his ear.

I know she aspirated it but does this sound typical for mast cell tumor under the skin?

Before I submit him to more surgery I want to get some feed back from those of you who have had diagnosed mast cell tumors of the skin.

I have no experience of this myself, but I'm bumping this up so hopefully someone who has can see it!