Sen. Edward M. Kennedy, D-Mass., center, is surrounded by family members Tuesday at the Massachusetts General Hospital in Boston. From left are son Rep. Patrick Kennedy, D-R.I., stepson Curran Raclin, son Edward Kennedy Jr., daughter Kara Kennedy and his wife, Vicki.

Washington ? Americans at all reaches of the political spectrum Tuesday reacted with shock and sadness – but also with hope – after Sen. Edward M. Kennedy, the last surviving brother of a tragedy-scarred political clan, was diagnosed with a malignant brain tumor.

The 76-year-old Massachusetts Democrat, a liberal giant of the Senate whose two older brothers were slain by assassins, remained hospitalized in Boston, surrounded by family members. Doctors revealed the diagnosis after they got the preliminary results of a brain biopsy.

The news hit Washington like a thunderbolt and ignited a nationwide outpouring of concern. Kennedy is the Senate’s second-longest serving member and has been a prominent figure in American politics for nearly a half-century.

“I’m having a hard time remembering a day in my 34 years here I’ve felt this sadly,” said Sen. Patrick Leahy, D-Vt. Senate Majority Leader Harry Reid, D.-Nev., called his colleague “an American icon.”

Kennedy is expected to remain in the hospital for at least two more days while his doctors determine a course of treatment. The tumor was diagnosed as a malignant glioma, a type of brain cancer that is diagnosed in about 9,000 Americans a year.

Kennedy, who was airlifted to the hospital after suffering a seizure at his Cape Cod home in Hyannisport on Saturday, underwent a number of tests over the past several days. Doctors said he has had no further seizures, remains in overall good condition and is up and walking around the hospital.

Kennedy’s wife, Vicki, and children have been with him each day since he was hospitalized.

President Bush was notified by his staff of Kennedy’s diagnosis at 1:20 p.m. In a statement, Bush described Kennedy as “a man of tremendous courage, remarkable strength, and powerful spirit.”

“Our thoughts are with Senator Kennedy and his family during this difficult period,” the president said. “We join our fellow Americans in praying for his full recovery.”

Kennedy’s Senate colleagues struggled with their emotions as they learned the news shortly after emerging from their regular weekly party lunches near the Senate chamber. The Senate’s longest-serving member, 90-year-old Robert Byrd, D-W.Va., cried and told colleagues he was “distraught and terribly shaken.”

“Ted, Ted, my dear friend, I love you,” Byrd said from behind his desk on the Senate floor. “Thank God for you, Ted. Thank God for you.”

“I would not be sitting here as a presidential candidate had it not been for some of the battles that Ted Kennedy has fought,” Sen. Barack Obama, D-Ill., who’s on track to become the first African-American presidential nominee of a major political party, told CNN.

Arizona Sen. John McCain, the presumptive Republican presidential nominee, was also among Kennedy’s well-wishers.

“I have described Ted Kennedy as the last lion in the Senate, and I have held that view because he remains the single most effective member of the Senate,” McCain said.

The diagnosis was the latest blow for a family and a man dogged by tragedy. President John F. Kennedy was assassinated in 1963, and his brother Robert was assassinated in 1968.

The family’s oldest son, Joseph P. Kennedy Jr., was killed when the airplane he was flying exploded during a mission to France in World War II. Kennedy himself was badly injured in a plane crash in Massachusetts in 1964, and one of his sons lost his right leg to cancer in 1973. John F. Kennedy Jr. was killed in a plane crash in 1999.