What is glioblastoma, the brain cancer John McCain has been diagnosed with?

As the news traveled quickly about Senator John McCain’s brain tumor diagnosis, CBS News chief medical correspondent joined CBSN’s “Red Blue” to explain what it means for the 80-year-old politician.

LaPook said that this is “a primary brain tumor” which started in McCain’s brain and that it didn’t spread there from somewhere else. The recent diagnosis surprised LaPook because the senator was in the hospital Friday to remove a blood clot from above his right eye — which at the surface seemed routine, LaPook said.

“I was quite surprised to find out that it was glioblastoma … a very serious type of brain tumor,” LaPook added. “The problem with glioblastoma is at the time that it is discovered, there are almost always microscopic cells that have spread elsewhere in the brain because it spreads along the nerve cells.”

Now with the statement out Wednesday night, the senator and his family are now reviewing further treatment options.

“The next thing to do would be chemotherapy, radiation,” LaPook said. “He’s in for a battle, this is a very serious kind of cancer and it’s the kind of cancer that killed Ted Kennedy. Despite all the research that’s been going on, we haven’t made adequate progress.”

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Some of the symptoms of glioblastoma, according to Dr. LaPook, include headache, general malaise, visual problems (including double vision).

In addition, speech problems are tied to glioblastoma. LaPook said that one possible example that may have been a precursor to the diagnosis was during the James Comey hearing last month. McCain faltered for words during the public hearing in front of the Senate Intelligence Committee.

LaPook said that McCain’s treatment could last four to six weeks and he could possibly return to the Senate depending on how he does, especially for his age.

“He’s battled melanoma, he’s battled being a prisoner of war and now this is his next battle,” LaPook said.