Argentina's President Cristina Kirchner underwent three-and-a-half hours of surgery for thyroid cancer and emerged without any problems, her spokesman said.
Kirchner had the surgery to remove her thyroid gland in the city of Pilar, 50 kilometres north of Buenos Aires.
"The operation was performed on the president without any problems or complications," spokesman Alfredo Scoccimarro said in front of Hospital Austral, where hundreds of supporters had gathered to show their support.
Kirchner awoke after the surgery and showed signs of a good immediate post-operative recovery, according to a statement from her surgeon, Pedro Saco.
President to resume her duties
Kirchner's cancer was discovered during a routine medical exam on December 22, only 12 days after she was sworn in for a second term as Argentina's president. She won re-election in October in a landslide victory.
She is scheduled to be hospitalised for 72 hours with a 20-day recovery period, during which vice-president Amado Boudou is taking over Kirchner's executive branch responsibilities.
The president, 58, arrived at the hospital Wednesday morning with her children Maximo and Florencia on board a helicopter.
Kirchner, the country's first elected female president, was diagnosed with cancer "on the right lobe of the thyroid gland," Scoccimarro said last week.
Doctors predicted she would be able to resume all of her duties as president.
Further growth of tumour unexpected
"The prospects are excellent and one would not expect any further growth of the tumour after the operation," said Mario Bruno, an oncologist and a member of the Argentina Association of Cancer.
Supporters camped out at the hospital put up posters that said, "Be Strong Cristina," along with flags and banners showing the faces of Kirchner and her deceased husband, Nestor, who preceded her as president.
Dozens of television camera crews, reporters and photographers had waited outside the hospital since Tuesday night in sometimes oppressive heat.
Security was spread over a wide area by members of the military police, Buenos Aires federal police and presidential security force.
Several Latin America leaders suffer from cancer
Kirchner is one of several Latin American leaders to suffer from cancer since 2009.
Venezuelan President Hugo Chavez, Brazilian President Dilma Rousseff and Paraguayan President Fernando Lugo have all waged battles against the disease and say they are now cancer-free.
Former Brazilian president Luiz Inacio Lula da Silva was diagnosed with throat cancer in late October and has undergone chemotherapy treatments. He re-entered a hospital this week for radiation therapy.
In a message of support to Kirchner made public by the Citizenship Institute he founded after leaving office, Lula expressed his great joy at the news that her surgery had gone well.
"We will soon meet again, both in good health," he said.
Chavez last week speculated that the United States could have developed a "technology to induce cancer" in Latin American leaders, without offering any evidence that such technology existed.
(Sapa, January 2012)