90 Year Old Mother Has A Cyst With Tunneling. Referred

90 year old mother has a cyst with tunneling. Referred to a surgeon who now has declined. What does "tunneling" mean? Cancerous? She is not in pain and can live with it....so she says. We live far away and don't understand the risks. Can you please shed some light on this for us? Thank you so much! God Bless