Argentine President Cristina Fernandez
Argentine President Cristina FernandezIsrael news photo: Presidency of the Nation of Argentina

Argentine President Cristina Fernandez, 58, has been diagnosed with thyroid cancer, and will undergo surgery January 4 to remove the tumor.

Test results showed Tuesday that the disease has not metastisized and is localized in a lobe in the right side of her neck. It has not spread to her lymph nodes, Afredo Scoccimarro, her spokesman said.

The cancer was discovered during a routine examination on December 22.

The usual treatment for thyroid cancer is to remove the tumor -- or as much of the cancerous material as possible -- and then to follow up with radioactive iodide treatment, taken orally, according to information on the website of the U.S. National Institutes of Health.

Oral radioactive iodide helps to destroy any remaining cancerous material, and also helps clarify imagery in followup studies to determine whether there are any remnants of the disease.

Patients who undergo surgery to remove thyroid cancer must take some form of thyroid hormone to replace that which is no longer produced by the thyroid gland removed during surgery, and regular blood levels are measured as well.

After surgery Fernandez will take a medical leave of 20 days, during which time the country will be led by Vice President Amado Boudou.

Earlier this year, Venezuelan President Hugo Chavez was also diagnosed with cancer and underwent surgery to treat the disease, followed by chemotherapy in Cuba as well.

President Fernando Lugo of Paraguay and President Dilma Rousseff of Brazil have both also undergone treatments for the disease recently as well, according to the Associated Press.