US Senator Edward M. Kennedy, the veteran lawmaker from Massachusetts who is the last surviving brother in the legendary Kennedy family, has been diagnosed with a malignant brain tumor, his doctors said today.

Experts in Boston and around the country said the information released indicated that Kennedy had terminal cancer and might have only a limited time to live.

Senator Edward M. Kennedy

Kennedy's doctors at Massachusetts General Hospital, who had been investigating the cause of a seizure that led to Kennedy's hospitalization this weekend, said that preliminary results from a brain biopsy indicated the seizure had been caused by a tumor in the top left portion of his brain.

The usual course of treatment for the tumor -- a "malignant glioma" -- includes combinations of various forms of radiation and chemotherapy, Dr. Lee Schwamm, vice chairman of the neurology department at the hospital, and Dr. Larry Ronan, Kennedy's primary care physician, said in a statement.

The doctors said decisions regarding the best course of treatment for the 76-year-old senator would be determined after further testing and analysis.

But other specialists said that the diagnostic details released by the hospital indicated that Kennedy had terminal brain cancer and most likely less than three years to live -- perhaps much less.

"Unfortunately, it's a really serious tumor," said Dr. Patrick Wen, clinical director for neuro-oncology at the Dana-Farber Cancer Center. Mass. General described the tumor as a malignant glioma, and that, Wen said, likely means that the tumor is at stage 3 or 4 on a four-point scale of severity, with 4 the most serious.

"The average survival for a Grade 4 tumor is 14 or 15 months," he said. "For a grade 3 tumor, it's two to three years. Unfortunately, the older you are, the worse it is. The biology of the tumor is worse, it's more aggressive."

Massachusetts General did not mention any plan to operate to remove the tumor, and specialists say that is probably because it is located in an area of the brain, the left parietal lobe, with many important functions, including speech and language. Tumors in this region can affect the ability to understand spoken and written words.

It is not clear how long Kennedy will be able to continue working, specialists say. Wen said that many patients do continue to work while undergoing treatment, which includes radiation and a type of chemotherapy pill that is generally well tolerated.

But Dr. Matthew Tilem, a Lahey Clinic neurologist, said, "I would think that most people receiving this diagnosis would retire in the near future."

Dozens of reporters, cameramen, and producers surrounded one of the entrances of Massachusetts General Hospital this afternoon, waiting for further word on Kennedy.

Kennedy's wife and children have been with him each day since he was hospitalized but have made no public statements.

The senator's wife, Victoria Reggie Kennedy, arrived today at Mass. General at 6:20 a.m., stepping out of a black sport utility vehicle and walking briskly inside. His sons -- Edward M. Kennedy Jr. and Representative Patrick Kennedy of Rhode Island -- came to visit their father at 9:45 a.m. None of the Kennedys talked to the media.

Senate Democrats and Republicans were in their separate weekly policy lunches when word reached them of the diagnosis. CNN reported there was stunned silence.

At a news conference after the meeting, Kennedy's fellow senators offered support.

Senator Harry Reid of Nevada, the Democratic leader, said he had talked to Kennedy's wife and the senator was in good spirits.

"The Senate really is a family," Reid said. "We, as a family, are tremendously concerned about Senator Kennedy."

Senator John F. Kerry, the junior senator from Massachusetts, said the Kennedys have faced more serious adversity more times than most families face once.

"Every one of us knows what a big heart this fellow has," Kerry said, calling his colleague a "living legend." "This guy is one unbelievable fighter ... He's in a fighting mood."

Malignant gliomas are a type of brain cancer diagnosed in about 9,000 Americans a year and are the most common type among adults.

Dr. Joseph Madsen, a neurosurgeon at Children's Hospital Boston, said the diagnosis was "very sad news."

“High-grade glio-malignancies” such as Senator Kennedy has “are unfortunately the most common kind of brain tumor in this age group, and they have a poor prognosis for long-term survival,” he said.

Kennedy's hospitalization Saturday triggered shock in the political world and drew an outpouring of support from around the nation. But the initial alarm subsided when friends and associates said that he was talking and joking with family later that day -- and watching the Red Sox game.

The youngest of the nine children of Joseph P. Kennedy and Rose Fitzgerald Kennedy, Edward Kennedy was first elected to the Senate in 1962 to finish the final two years of his brother's term. He is serving his eighth term and is the second most senior member of the Senate.

A champion of liberal causes, he unsuccessfully ran for president in 1980, losing the Democratic nomination to President Carter.

(George Rizer/Globe Staff)

Senator Edward M. Kennedy's sons -- Edward M. Kennedy Jr. (left) and Representative Patrick Kennedy of Rhode Island -- arrived today at Massachusetts General Hospital at 9:45 a.m

Material from The Associated Press was used in this report.