Mr. Kennedy’s physicians issued a statement saying “preliminary results from a biopsy of the brain identified the cause of the seizure” he suffered Saturday “as a malignant glioma in the left parietal lobe.”
The doctors did not comment directly on Mr. Kennedy’s prospects for recovery, but glioma is one of the most common causes of cancer deaths. It is the most common form of brain cancer, accounting for more than half of the more than 18,000 brain tumors diagnosed each year in the U.S.
Video:Kennedy weighing medical options
The Associated Press quoted Dr. Keith L. Black, chairman of neurosurgery at Cedars-Sinai Medical Center in Los Angeles, saying that without surgery, a typical glioma patient of Mr. Kennedy’s age would be “probably looking at a survival of less than a year.”
The grim diagnosis, which prompted an outpouring of emotion on Capitol Hill, followed a series of tests over the past several days to determine the cause of a seizure that struck the 76-year-old liberal warrior as he was having breakfast at the Kennedy family compound in Hyannisport, Mass.
“The usual course of treatment includes combinations of various forms of radiation and chemotherapy. Decisions regarding the best course of treatment for Senator Kennedy will be determined after further testing and analysis,” said a statement issued jointly by Dr. Lee H. Schwamm, vice chairman of the Department of Neurology at Massachusetts General, and Dr. Larry Ronan, the senator’s primary care physician.
“He has had no further seizures, remains in good overall condition, and is up and walking around the hospital. He remains in good spirits and full of energy,” the doctors said. He was expected to remain at the hospital for the next couple of days.
The news of Mr. Kennedy’s illness stunned official Washington.
“Politics almost completely stopped today. This is a story that every American at some level will be involved in emotionally because of the impact the Kennedy family had on America,” said former Democratic National Committee Chairman Steve Grossman, a longtime Kennedy friend in Boston.
Statements wishing the last surviving brother of the Kennedy dynasty a full recovery poured in yesterday from his political supporters and adversaries alike.
Sen. Barack Obama, the Democratic presidential front-runner whose candidacy received a well-timed Kennedy endorsement earlier this year, called the news “heartbreaking.”
“Ted Kennedy not only is a giant of the Senate but he’s a great friend to all of us. He couldn’t be a better friend of mine and a better supporter,” Mr. Obama said. “Obviously this is grim news.”
Sen. Hillary Rodham Clinton, whom Mr. Kennedy did not endorse even though she easily won his state’s Democratic primary, said in a terse two-sentence statement that “Our thoughts are with him and [wife] Vicki and we are praying for a quick and full recovery.”
Sen. John McCain, the presumptive Republican presidential nominee, called Mr. Kennedy “the last lion in the Senate.” Mr. McCain joined forces with Mr. Kennedy in an ill-fated immigration reform bill that would have opened a path to citizenship for illegal immigrants.
A frail Sen. Robert C. Byrd, who at 90 is the chamber’s oldest member, broke down in tears on the Senate floor as he offered “my heart and my humble prayers” for the second-longest-serving member of the Senate. Choking back tears, the West Virginia Democrat said, “Ted, Ted, my dear friend, I love you and I miss you.”
Sen. John Kerry, who visited his fellow Massachusetts Democrat over the weekend, said, “He’s in a fighting mood. … I know that Ted is determined to fight this.”
Mr. Kennedy has not been seen in public since his seizure, but he has called some of his closest colleagues from his hospital room.
“My cell phone rang and I picked it up and here was this voice that sounded terribly familiar to me talking about how those nurses were picking on him up in that hospital. It had me laughing,” Sen. Christopher J. Dodd, Connecticut Democrat, told reporters.
The senator received some optimistic advice from Sen. Arlen Specter, who was diagnosed with a malignant brain tumor in 1993. “I’ve been there,” the Pennsylvania Republican said on the Senate floor yesterday.
Mr. Specter said he was “given three to six weeks to live,” but “the diagnosis … turned out to be incorrect.” Surgeons removed what turned out to be a benign tumor from the senator, who is fighting his second bout of Hodgkins disease and undergoing chemotherapy.
Glioma tumors are the second most common cause of cancer deaths in people ages 15 to 44, cancer specialists say. Survival rates can range from a year or less for the most severe cases to five to 10 years for slower growing, less aggressive tumors.
• Steven A. Miller and Christina Bellantoni contributed to this story.