I had a right frontal lobe meningioma in 2001. Because of the size of mine (5cm, about the size of a small orange) I was also told that it had probably been there for at least 20 years. I found out about mine by having a grand mal seizure out of the blue. Because it caused a seizure and because there was no way to know if it was benign without surgery, I had mine surgically removed. Fortunately it was benign. I had two small recurrences in 2017 and had gamma knife radiation on them at Mayo in Rochester. How did your doctor know it was benign? Did you have a surgical biopsy?