Senator John McCain (R-Arizona) is eager to get back to work.

Wednesday night, it was announced that he was diagnosed with an aggressive form of brain cancer. Doctors say it's a Glioblastoma tumor.

McCain is an active 80-year-old, but this kind of tumor might slow him down.

"This is a very aggressive spreads very easily. And again, it has a low survival rate," said NBC Medical Correspondent, Dr. John Torres, "[These] treatments are going to affect him to a certain extent that he might get back to work part-time, but full time, that would essentially be icing on the cake."

But even Dr. John knows McCain won't go down without a fight.

"Best case scenario: this disease, he ends up tackling it, he gets back to work full time in the Senate....One thing we know about Senator McCain is he is an extreme fighter. He's going to do what he can to fight this cancer."

McCain has been recuperating at his home in Arizona.