My mother (61 years old) has had a cyst on the back of her neck for 25-30 years. About 25 years ago, she had it drained. She has not done anything to it since. Back then it was the size of a marble. It is now the size of a baseball. Within the last year it has gotten a black spot in the center of it. The center of it has a small indention, maybe it is where they drained it years ago. The black spot is in the location of that mark. The cyst does not drain. I would like to know if it is possible for a cyst to become cancerous. She does not want to go to a doctor, but I am very worried. Could someone please help me with this? Thank you!