Argentina's president Cristina Fernandez has been diagnosed with thyroid cancer and will undergo surgery Jan. 4.

Fernandez, 58, will take 20 days of medical leave, her spokesman Alfredo Scoccimarro said. Vice president Amado Boudou will be in charge during her absence.

Scoccimarro said the cancer was discovered during a routine exam on Dec. 22, and that Fernandez received the results from follow-up tests hours before the announcement.

This kind of thyroid cancer is highly survivable, with more than 95 per cent of patients living at least 10 years after detection, according to the U.S. National Institutes of Health.

The usual treatment is to surgically remove as much of the cancerous material as possible, and then follow up with radioactive iodide treatments, taken orally. This substance helps to destroy any remnants of the cancerous gland and provide for clearer images showing any additional cancer, the NIH said on its Web site.

Fernandez was a senator during the presidency of her husband, Néstor Kirchner, who stepped down in 2007. Fernandez ran to succeed him and was elected, becoming the first elected female president of Argentina.

Her husband died of heart failure in 2010. She was re-elected in October by a wide margin and sworn in Dec. 10.

During her first four-year term, economic expansion averaged 5.6 per cent a year, aided by soybean exports and growth in Brazil, Bloomberg News reported.

Consumer boom

Fernandez used record government revenue to boost spending on public works, raise pensions and give cash handouts to poor families. The expenditures contributed to a consumer boom and helped fuel inflation that economists estimate at an annual 25 per cent, Bloomberg said.

Fernandez is only the latest South American leader to be diagnosed with cancer. Presidents Fernando Lugo of Paraguay, Hugo Chavez of Venezuela and Dilma Rousseff of Brazil all have undergone treatments recently.

Presidential doctors Luis Buonomo and Marcelo Ballesteros said the operation will be led by Dr. Pedro Saco, chief of the surgery department at Hospital Austral and chief of the Head and Neck Service of the oncology institute at the University of Buenos Aires.

Saco also trained in cancer centers in Houston and New York, the hospital said.

Thyroid surgery is not without risk: the NIH says a nerve that controls the vocal cords can be damaged, and doctors sometimes accidentally remove the parathyroid gland, which helps regulate blood calcium levels.

With files from The Associated Press