Senator Edward Kennedy waves as he leaves Massachusetts General Hospital in Boston Tuesday. (CBC)

Accompanied by friends and family, Senator Edward Kennedy slowly walked out of a Massachusetts hospital Wednesday, a day after being diagnosed with a cancerous brain tumour that experts say is almost certainly fatal.

A crowd of well-wishers applauded the 76-year-old Democrat as he emerged from the doors of Massachusetts General in Boston. He smiled, waved back and gave a thumbs-up. His dogs greeted him at the hospital door.

His doctors say Kennedy "has recovered remarkably quickly" from a biopsy conducted after he suffered a seizure last weekend.

They say he will await further test results and treatment options while convalescing at home on Cape Cod over the U.S. Memorial Day weekend.

The last son of one of America's most famous political families was diagnosed with a malignant glioma in his left parietal lobe after suffering a seizure in his home on Saturday.

Malignant gliomas are diagnosed in about 9,000 Americans a year.

In general, half of all patients die within a year.

Kennedy's wife, Vicki, told friends the grim diagnosis was "a real curveball" that left his family stunned even as he joked and laughed with them, but she expressed pride in how her husband was handling the news.

"Teddy is leading us all, as usual, with his calm approach to getting the best information possible," she wrote in an e-mail Tuesday to friends.

"He's also making me crazy (and making me laugh) by pushing to race in the Figawi this weekend," she wrote, referring to the annual sailing race from Cape Cod to Nantucket.

The diagnosis cast a pall over Capitol Hill, where the Massachusetts Democrat has served since 1962, with members from both sides of the aisle reacting emotionally to the news.

With files from the Associated Press