A woman so horribly disfigured she was willing to risk her life to do something about it has undergone the nation’s first near-total face transplant, the Cleveland Clinic announced Tuesday.

Reconstructive surgeon Dr. Maria Siemionow and a team of other specialists replaced 80 percent of the woman’s face with that of a female cadaver a couple of weeks ago in a bold and controversial operation certain to stoke the debate over the ethics of such surgery.

The patient’s name and age were not released, and the hospital said her family wanted the reason for her transplant to remain confidential. The hospital plans a news conference today.

The transplant was the fourth worldwide; two have been done in France, and one was performed in China.

Details of the Cleveland surgery were not disclosed, but surgeons generally transplant skin, nerves and muscle, and often other deep tissue. That is done so that the new face will actually function and not just be a mask.

Surgeons not connected to the case reacted cautiously since little was known about the circumstances, but they generally praised the operation.

“There are patients who can benefit tremendously from this,” said Dr. Bohdan Pomahac, a surgeon at Harvard-affiliated Brigham and Women’s Hospital in Boston who plans to offer face transplants, too.

Unlike operations involving vital organs, transplants of faces or hands are done to improve quality of life — not extend it. Recipients run the risk of deadly complications and must take immune-suppressing drugs for the rest of their lives to prevent organ rejection, raising their odds of cancer and other problems.

Siemionow, (pronounced SIM-en-now), 58, a noted hand microsurgeon, has been testing the surgical approach and ways to temper the immune system’s response in experiments for more than a decade.

She considered dozens of burn victims and other potential candidates over the past four years, ever since the clinic’s internal review board gave her permission to attempt the operation. She said she would choose someone severely disfigured as her first case.

The world’s first partial face transplant was performed in France in 2005 on a 38-year-old woman who had been mauled by her dog. Isabelle Dinoire received a new nose, chin and lips from a brain-dead donor. She has done so astoundingly well that surgeons have become more comfortable with a radical operation considered unthinkable a decade ago.