GREENSBORO, N.C. - Sun Ming Ming’s hands are enormous. He catches a basketball with one hand, as a baseball player might with a mitt. They are hands with the touch of a shooting guard, able to sink one 20-foot jumper after another.

Sun is no guard — at nearly 7-foot-9, he would be the tallest player in NBA 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 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 387 pounds and has a 50-inch 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 extreme northeastern China, Sun grew up poor and in middle school was sent to a state-run basketball academy. He played on a lower-level pro team, but didn’t have access to quality medical care.

Had he lived in the U.S., there’s little chance his condition would have gone untreated for so long, said Stephen Tatter, a neurosurgeon at Wake Forest’s Baptist Medical Center.

“It’s the kind of thing that if you saw a kid who was growing that fast, you would kind of walk over and hand his parents a card and tell them to come and see me,” Tatter said.

Chris Keane / Reuters file That's some grip! China's Sun Ming Ming has a nice shooting touch with a fluid stroke.

Without treatment, it wasn’t only Sun’s basketball career that was threatened. Tatter’s partner at Wake Forest’s Gamma Knife Center, Volker Stieber, said patients with acromegaly tend to die from heart failure at a young age, usually in their 30s or 40s.

“To put it simply, they tend to outgrow their hearts, so to speak,” Stieber said.

Manning, who owns a packaging company, footed most of the $100,000 bill 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 Sun’s optic nerve and they feared he could go blind.

Late last month, Stieber and Tatter performed a second, knifeless surgery on Sun 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.

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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.

“He’s lifting weights, running, stretching and playing basketball,” Manning said. “His stamina, the way he feels, the way he acts, is totally different, like night and day.”