Media is already speculating on Kennedy's replacement. I think he will stay until the very end tho

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 described the tumor as a malignant glioma; Wen said that probably means 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."

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."