Shanghai, Dec. 9 -- SUN Mingming's hands are enormous. While they are big enough to catch a basketball with one hand, they are similar to those of a shooting guard, able to sink one 20-foot jump shot after another.

Sun is no guard - at nearly 2.36 meters, he would be the tallest player in National Basketball Association history. But the pituitary tumor that led to his extraordinary size is threatening his life and keeping him away from a pro basketball career.

He recently underwent a second operation, though it could be years before Sun and his doctors find out if it was a success. Until then, he's doing what he can to prepare his body for the rigors of pro sports.

"When he first came here, he acted like a 60-year-old man," said Rocky Manning, who allowed Sun to stay with his family in Greensboro, North Carolina, when he moved from China to the United States nearly two years ago. "He sat around and didn't say much. He had a hard time just raising his arm above his head. If he would hold onto the net it would hurt. He hated dunking the ball."

The 23-year-old Sun has acromegaly, a condition caused by a tumor that leads his pituitary gland to overproduce growth hormone. It's why Sun is not only so tall, but weighs 175 kilograms and has a 127-centimeter waist, a size that puts tremendous pressure on his joints. The tumor also limits testosterone production - which means he lacks strength, stamina and speed.

"In China, I would get tired running," Sun said. "I didn't know until I came here that I have a tumor."

It's rare that a case of acromegaly is diagnosed so late. A native of Harbin in northeastern Heilongjiang Province, Sun grew up poor and in middle school was sent to a state-run basketball academy.

Manning, who owns a packaging company, footed most of the US$100,000 cost for Sun's first surgery last year, but doctors in Los Angeles only were able to remove part of the tumor because it was wrapped around his optic nerve and they feared he could go blind.

Late last month, Sun underwent a second, knifeless surgery called gamma knife radiosurgery. It involved beaming a targeted dose of radiation through the skull, and it's hoped that within one to three years the tumor will dissolve and his hormone levels will become normal.

Manning said Sun's stamina improved greatly after the first surgery, when he was able to lift weights for the first time in his life. Following the second procedure, Manning said, Sun is able to train for six to seven hours a day.

NBA executives have shied away from Sun because of his medical problems, but his size alone could raise interest if the second surgery is a success.