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. Specialists in Boston and around the country said the information released indicated that Kennedy has terminal cancer and might have only a limited time to live. 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 has 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 Institute. Mass. General's description of the tumor as a malignant glioma probably means the tumor is at stage 3 or 4 on a four-point scale of severity, with 4 the most serious, Wen said.. "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." Mass. 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." Boston Globe photographer Bill Greene said Senator Kennedy and his family made small talk during a brief photo opportunity today in a small lounge inside Massachusetts General Hospital. "The senator remained seated. He seemed in good spirits," said Greene. He said Kennedy's daughter Kara sat close to the senator with her hand on his knee. "At one point, Kennedy let out a laugh," said Greene. Meanwhile, outside the hospital, dozens of reporters, photographers, and producers gathered, waiting for further word on the senator. Senate Democrats and Republicans were in their separate weekly policy lunches when word reached them of the diagnosis. CNN reported there was stunned silence. Local, state, and national elected officials expressed support. Senator John F. Kerry, the junior senator from Massachusetts, said the Kennedys have faced serious adversity more times than most families. "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." Governor Deval Patrick said, "I know I speak for people all over the Commonwealth, indeed all over the country, wishing him well and sending him the very best and strongest prayers." "You don't have time and enough tape for all the different ways in which Ted Kennedy has, and continues to be, important to Massachusetts. His interests in the meek and the mighty, for economic justice, health care, education. He has an extraordinary record, and I'm looking forward to continuing to work with him," Patrick said. People interviewed this afternoon in Boston's Back Bay area also expressed shock and offered their sympathy. "Someone who has given 40 years of service -- that's pretty remarkable. My prayers are with him and his family," said Price Blair, 28, of Boston, a postdoctoral researcher. "It's hard to imagine Capitol Hill without him." "He's been a part of the country's fabric for decades," said Eric Lass, 40, a financial analyst from Newton. "He's the final brother." 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 the term of his brother, John F. Kennedy, who had been elected president. Edward Kennedy 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.