|Cristina Fernandez de Kirchner announced her cancer diagnosis in the last week of 2012 [Reuters]|
Early on Wednesday, Cristina Fernandez de Kirchner, 58, flew by helicopter from the presidential residence in Olivos to the Hospital Austral in suburban Pilar, north of the capital Buenos Aires.
She went under general anesthesia several hours later for the operation led by Dr Pedro Saco, a veteran Argentine oncologist who specialises in cancers of the head and neck.
Vice President Amado Boudou was put in charge shortly before the operation, and will remain as the country's constitutional leader for 20 more days while Kirchner takes medical leave, the presidency said.
"Cristina's operation was successful," TV station Cronica said during a news broadcast. Doctors said they would be able to report surgery results by midday.
Supporters gathered outside the hospital waving signs showing Fernandez de Kirchner and her late husband, former President Nestor Kirchner, who died of a heart attack in 2010.
Fernandez de Kirchner was found to have papillary thyroid carcinoma shortly after beginning her second four-year term as Argentina's leader, doctors said.
Preoperative tests suggested it had not spread beyond her thyroid, so the condition should be curable without chemotherapy, they added.