Mary Clancey said she was resigned to being a plump old lady after 15 years of steadily increasing weight. But with her health deteriorating, her son persuaded her to go to hospital in Pennsylvania for tests.

What doctors found astounded them - a cyst in one of her ovaries had grown into the huge tumour.

Doctors at Lehigh Valley Health Network in Allentown operated on Ms Clancey in November.

Going in, she weighed more than 26 stone. After five hours in surgery, she lost nearly 13 stone of tumour and tissue.

The woman from St Clair, Pennsylvania, spent almost a month in recovery but is now back home. She now weighs around 10 and a half stone.

Ms Clancey said of her tumour: "You can't imagine in your wildest dreams something that huge."

As she was gaining weight, Ms Clancey said doctors told her just to watch what she ate. At just over 5ft tall, she felt destined to become "a short, round, fat little old lady".

She told Philadelphia TV station NBC10 that the tumour did not really cause her pain. "It just made itself comfortable in there," she said.

But by the time she went to the hospital, it had become difficult to walk or even stand.

Dr Richard Boulay, who performed the operation, said the mass was so big it did not even fit in the picture taken by a CT scan.

"It was slowly killing her," Dr Bouley said.

To help in the removal of the tumour, a second table had to be moved next to the one on which Ms Clancey was lying so the mass could be rolled out without rupturing, The Morning Call reported.

Made up predominantly of water, the tumour was "slippery and nasty", Dr Boulay said.

Ms Clancey said she now "feels great".