Senator John McCain has been diagnosed with a brain tumor, his office said in a statement Wednesday.

The 80-year-old lawmaker has glioblastoma, according to doctors at the Mayo Clinic in Phoenix, where McCain had a blood clot removed from above his left eye last Friday.

What is 'glioblastoma' and how aggressive is it? Does age play a factor in the treatment? And did the condition play a factor in McCain's confusing round of questions at James Comey's hearing before the U.S. Senate last month?

WKYC Channel 3 anchor Russ Mitchell asked these questions and more to Dr. Andrew Sloan, neurological surgeon and Director, Brain Tumor and Neuro-Oncology Center at University Hospitals. You can see the interview above.