Some surgeons in the United States also have begun using the procedure, The Wall Street Journal reported Tuesday.

Advocates say the procedure, which uses fat harvested from elsewhere in a woman's body fortified with stem cells, results in breasts that look and feel more natural than those with silicone implants. But doctors worry the procedure may produce long-term problems, including breast cancer.

Surgeons have tried to use fat to enlarge breasts for decades. But the fat would die.

Advocates say stem-cell fortification allows the fat to develop blood vessels. Because the injected substance comes from the patient's body, she will not reject it.

The Food and Drug Administration has not yet made a decision on the procedure. The FDA has no jurisdiction over surgical procedures but says fat mixed with stem cells would come under its purview.