What are the advantages and disadvantages of getting a biopsy?

If it was my mom, I'd let it go. She's made her wishes known and it doesn't sound like she'd want it removed or any further treatments if it was something like cancer. You wouldn't need hospice until it looks like she's coming to the end of her life, but it doesn't sound like that is close to happening. My dad had a very large fatty cyst on his back and his doctor just kept an eye on it. He died at 92 from lung cancer and the cyst played no part.

Depends where it is and how deep it is. Why not at least have it drained?

I agree but I'm worried the cyst in her neck will obstruct her breathing and eating at some point. Do I need Hospice to help with everything?

My thought would be that the only reason to get a biopsy would be to develop a treatment plan ie: surgery, chemo, meds, etc. If you and your Mom are comfortable with a decision not to do anything what deference does it make what this cyst is? Has her doctor given both her and you a possible outcome of a "do nothing" approach for this cyst? The world of medicine is wonderful but it is often unrealistic. My Mom is a 90yo with advancing dementia and is still notified yearly that it's time for her mammogram. If something were to show up there is no way we would agree to surgery, chemo or radiation. So what is the point of having a mammogram done. Sometimes family needs to step up in the best interest of the family member and just say no.

That's a tough question. I know some of us are scare to even have a biopsy thinking the worse, when in fact, it could be something very simple and easy to take care of us. It's the fear of the unknown.

Tell your Mom that at 85 she is still young... my Mom is 97. Ask her if she could get the biopsy for you, to help you rest easier.