Dr. Greg Gores said the rapid nature of Walter Payton's cancer, which spread outside his liver, made a transplant impossible.

The clue was that Payton was both gaunt and jaundiced -- a sure sign Payton not only had primary sclerosing cholangitis but bile duct cancer as well.

As late as the day before he died, Payton's friends and family denied the NFL career rushing leader was gravely ill and said his condition had not deteriorated enough to make him eligible for a new liver.

But liver specialists said they were sure Payton was, in fact, dying.

"Survival once you get this (bile duct cancer) is about 11 months," said Dr. John Brems, director of intrabdominal transplantation at Loyola.

Dr. Greg Gores, who was treating Payton at the Mayo Clinic in Rochester, Minn., said the cancer killed Payton. Gores would not say when Payton learned he had cancer.

"The malignancy was very advanced and progressed very rapidly," Gores said at a news conference. "Because of the rapid nature of his cancer, the cancer spread outside his liver. At that point, liver transplant was no longer tenable."

But judging by Payton's appearance, liver specialists speculated he knew of his cancer at the time he announced he would need a transplant.

"Survival once you get this (bile duct cancer) is about 11 months," said Dr. John Brems, director of intrabdominal transplantation at Loyola.

"My guess is he knew he wasn't going to get a transplant," Van Thiel said.

Payton had a disease that scars the bile ducts, which carry bile from the liver to the small intestine to help digest food. When the ducts get blocked, bile backs up and migrates elsewhere.

Van Thiel explained that PSC is characterized by acute inflammation of the bile ducts inside and outside the liver.

"There is a replication of cells and sooner or later there's going to be an error in that replication and a cell is going to be an abnormal cell, a cancer cell," Van Thiel said. He said the cancer that killed Payton occurs in about 10 percent of PSC cases.

Once a PSC patient has cancer, doctors say, a liver transplant is no longer an option. Doctors often call off liver transplants if they find bile duct cancer, because the drugs needed to keep the body from rejecting the new liver make tumors grow faster.

"It's like adding gasoline to a fire," Brems said. "You're trying to suppress the immune system (for the new liver) and you need to stimulate immune system to fight the cancer."

Sometimes doctors don't see the tumors and unwittingly transplant livers in patients with the cancer. "One out of 10 survive two years," Brems said.