His 186-pound tumor is record-breaking, but the size of his smile is what's really remarkable about Nguyen Duy Hai.

The 31-year-old Vietnamese man has had a tumor growing on his right leg since soon after he was born.

Despite having an amputation at the knee 14 years ago, he still has a growth wider than three feet. 

"I can't do anything; I can only sit and lie down," he said in his home in the town of Da Lat in the country's Central Highlands.

The tumor is the largest ever documented in Vietnam, Vu Van Thach, head of examination department of Hanoi hospital, told German press agency DPA.

Hai's family are too poor to afford another operation after the amputation in 1997 failed to stop the growth, and now he is appealing for funds to afford medical help.

The tumor is non-cancerous and could be due to a genetic mutation, doctor Vu Van Thach said.

"If it was malignant he would not be alive now," he said.

Click here to read more on this story from the Herald Sun.