Nguyen Dua Hai from Vietnam has a tumour that measures 1.2 meters in diameter and weighs up 90kg.
The 31-year-old from the town of Da Lat is unable to move and can only sleep sitting up.
His mother, 61, has reportedly taken care of all of her son's basic needs. She told Tuoitrenews that she worries her declining health won't let her do that anymore.
Hai was born a normal child but developed the tumour soon after.
When he was four years old, his right leg showed abnormal signs of growing much faster than the left.
At 17, the tumour weighed about 25kg. He then had an amputation at the knee at Lam Dong General Hospital.
Doctors at the hospital could not diagnose the cancer.
According to the Vietnamese newswire, the tumor suffered from cracked skin and necrosis.
In 2001, the amputated leg developed a tumor again, which kept growing until its current size of 1.2 meters.
The swelling spread to his lower body and back. Hai now has to struggle everyday with his own body and suffers from excruciating pain.
In the latest update Hai's tumour has begun to bleed severely from a 5cm-long crack in the growth.
Doctors at Da Lat's Hoan My hospital told media that the tumour 'stretched' and cased a crack in it.
Fortunately the wound would not affect his health or a scheduled surgery on November 18.
Vietnamese and US surgeons are scheduled to operate on Nguyen Duy Hai on November 18 at Ho Chi Minh City Tumor Hospital.
The surgery is expected to last 10-12 hours.