Sen. Edward Kennedy is surrounded by family members, left to right, son Patrick Kennedy, stepson Curran Roclin, son Edward Kennedy Jr., daughter Kara Kennedy and his wife Vicki at the Massachusetts General Hospital. (Stephan Savoia/Associated Press)Doctors treating Edward Kennedy said Tuesday that the U.S. senator has a malignant brain tumour, a grim diagnosis that was greeted with get-well wishes from his colleagues.

The tumour was discovered after Kennedy had a seizure at his family vacation home on Cape Cod on Saturday and was taken by air ambulance to Massachusetts General Hospital in Boston.

A statement released by medical staff at Massachusetts said tests had found a tumour known as a glioma on the left side of his brain.

His treatment will be decided after more tests, but the usual course includes combinations of radiation and chemotherapy.

The 76-year-old senator has his wife and children with him, and the statement released by the hospital said he was watching baseball on television and relaxing with his family.

"He has had no further seizures, remains in good overall condition, and is up and walking around the hospital," the hospital statement said. "He remains in good spirits and full of energy."

Senator Edward Kennedy, shown in 2006, has been diagnosed with a tumour known as a glioma on the left side of his brain. (Evan Vucci/Associated Press)Kennedy will remain at the hospital for the next couple of days according to routine protocol, hospital officials say.

CBC's Henry Champ in Washington says doctors are making a connection between Kennedy's current condition and an operation six months earlier to remove a blockage from the senator's carotid artery.

"The news is depressing to say the least," reports Champ. "The prognosis for the future is not good."

'Strength and powerful spirit'

U.S. President George W. Bush issued a statement Tuesday saying both he and his wife, Laura, were concerned to learn of Kennedy's diagnosis.

"Ted Kennedy is a man of strength and powerful spirit," the statement said. "Our thoughts are with Senator Kennedy and his family during this difficult period. We join our fellow Americans in praying for his full recovery.

Kennedy's colleagues were also quick to offer get-well wishes following news of his diagnosis.

House Speaker Nancy Pelosi said Kennedy's son, Patrick, telephoned her with the news.

“That news has been met throughout the country with great concern,” she said. "I have confidence though because Senator Kennedy has been a fighter all his life.”

Fellow Massachusetts Senator John Kerry said Kennedy was in a "fighting mood" during a visit in hospital over the weekend. Kerry also urged people to respect the privacy of the Kennedy family during this difficult time.

"I think that one of the most important things here for all of us to try to do is to remember that even as this man who is a living legend, who represents so much of our history, is going through this, we all need to try to give the family privacy," said Kerry.

Survival rate varies

Malignant gliomas are a type of brain cancer diagnosed in about 9,000 Americans a year — and the most common type among adults. How well patients fare depends on what specific tumour type is determined by further testing.

Average survival can range from less than a year for very advanced and aggressive types, to about five years for different types that are slower growing.Edward Kennedy and his wife Vicki sit together in a family room at the Massachusetts General Hospital. (Stephan Savoia/Associated Press)

"As a general rule, at 76, without the ability to do a surgical resection, as kind of a ballpark figure you're probably looking at a survival of less than a year," Dr. Keith Black, chair of neurosurgery at Cedars-Sinai Medical Center in Los Angeles, told the Associated Press.

Kennedy is the second-longest serving member of the U.S. Senate, after Robert Byrd of West Virginia.

Kennedy was first elected in 1962. He is the most prominent surviving member of the Kennedy clan.

Both his elder brothers, President John F. Kennedy and Senator Robert Kennedy, were assassinated in the 1960s, and his own political career was set back in 1969 when he was at the wheel of a car that flipped off a bridge, killing a young woman passenger, Mary Jo Kopechne.

Kennedy fled the scene and didn't report the accident until the following day, which resulted in a suspended jail sentence.

Since then, he has run for president once in 1980, and positioned himself as the leader of liberal politics in the U.S. Senate.

With files from the Associated Press