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John McCain’s brain tumor is particularly aggressive type

FILE - In this June 22, 2017, file photo Sen. John McCain, R-Ariz., arrives for a Senate Republican meeting on a health reform bill on Capitol Hill in Washington. McCain has been diagnosed with a brain tumor after doctors removed a blood clot above his left eye last week, his office said in a statement July 19. (AP Photo/Andrew Harnik, File)
FILE - In this June 22, 2017, file photo Sen. John McCain, R-Ariz., arrives for a Senate Republican meeting on a health reform bill on Capitol Hill in Washington. McCain has been diagnosed with a brain tumor after doctors removed a blood clot above his left eye last week, his office said in a statement July 19. (AP Photo/Andrew Harnik, File) FILE - In this June 22, 2017, file photo Sen. John McCain, R-Ariz., arrives for a Senate Republican meeting on a health reform bill on Capitol Hill in Washington. McCain has been diagnosed with a brain tumor after doctors removed a blood clot above his left eye last week, his office said in a statement July 19. (AP Photo/Andrew Harnik, File)

WASHINGTON (AP) – Sen. John McCain’s tumor is one of the most aggressive forms of brain cancer, and his family and doctors are deliberating next treatment options.

The senator had undergone surgery last week to have a blood clot removed from above his left eye, and that clot turned out to be a sign that a tumor called a glioblastoma had begun growing.

Here are some things to know:

AGGRESSIVE CANCER

McCain’s doctors at the Mayo Clinic said they managed to remove all the tumor that was visible on brain scans. But this kind of tumor, formally known as a glioblastoma multiforme, is aggressive and sneaky. It puts out microscopic roots that go deeper into brain tissue, explained Dr. Joshua Bederson, chairman of neurosurgery at Mount Sinai Health System in New York, who has no direct knowledge of McCain’s care.