Surgeons removed a man's tumour and rebuilt his body using leg muscles and tissue they had removed and attached to his arm to keep alive.
The operation on Sunderland man Ian McGregor lasted 18 hours and is thought to be the first of its kind in the UK.
Surgeons in Newcastle took his calf, attached it to his arm and then used it to repair the site of the operation.
The 59-year old, who is making a good recovery, said: "You just can't put into words what they did."
The large aggressive tumour had spread from Mr McGregor's pelvis into his thigh. Previous attempts had been made to treat the cancer over the past 10 years but had been unsuccessful.
For the latest attempt, surgeons feared the hole left would be too big to repair.
Then the team at Newcastle's Freeman Hospital came up with the idea to remove his lower leg, except for the bones, and attach it to his forearm - thereby maintaining the blood flow.
After removing his leg and the tumour they then disconnected the calf from his forearm and used it to repair the area from where the tumour had been removed.
The surgery last August started at about 09:00 and lasted until after 03:00 the following morning.
When they first told Mr McGregor what was going to be done, he thought it was "Star Trekky".
He said: "I couldn't imagine what they were telling me, how they would do it and if I would wake up from the operation."
He said he had been given the choice about whether to have the operation but believed if he had not he would no longer be here. He said at the time he was in pain 24 hours a day.
He described what the surgeons had achieved as "amazing" and said he could not thank them enough.
"You can't describe the feeling, you think you're at death's door and then you wake up and think wow, I'm here. It's a wonderful feeling," he said.
The experts at the Newcastle hospital believe it may be the first operation of its kind in the world - they understand it may have been attempted in the US but over the course of two operations.
Three consultant specialists worked together on the plan.
Consultant Plastic and Reconstructive Surgeon Mani Ragbir said it was very unusual.
"We are not aware of anyone having done this particular procedure before," he said.
"It's not easy for a surgeon to tell a patient that they haven't done this particular procedure before."
They now plan to publish their work and believe it may open up a new approach to surgery.