I had one that started in my 30s between my neck & shoulder, it was slow growing but grew to about the size of a fist. I had it removed about 10 years ago because it was causing all sorts of problems giving me frozen shoulder like symptoms and headaches.
I had local anaesthetic but was on the cusp of them having to put me under, it was growing around nerves and the surgeon struggled to get it all out. He said no wonder I was in so much pain. I don’t think he got it all, I’ve been back as it’s starting to grow again but he’s very reluctant to go back in because he says there’s a lot of scar tissue from last time. He also said that now they only remove them if they are causing problems, they don’t do them now for cosmetic reasons so wouldn’t do it for that reason also
I do have tiny pea size ones in other places on my body that never grow any bigger, the one on my hip I’ve had since my teens so over 50 years