Argentina's president Cristina Fernandez has thyroid cancer, but test results show that it remains limited to a lobe in the right side of her neck and has not metastasised or spread into her lymph nodes, her spokesman said.
Alfredo Scoccimarro said the cancer was discovered during a routine exam on December 22, and that Ms Fernandez received the results from follow-up tests hours before the announcement.
He said Ms Fernandez will undergo surgery on January 4 at the Hospital Austral in Buenos Aires and then take 20 days of medical leave, during which Vice President Amado Boudou will run the country.
Ms Fernandez, 58, will keep up her normal routine meanwhile, Dr Scoccimarro said, noting that she will appear at several events as planned.
This kind of thyroid cancer is highly survivable, with more than 95% of patients living at least 10 years after detection, according to the US National Institutes of Health (NIH).
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 website.
After surgery, patients must usually take medicine for the rest of their lives to replace a hormone that the thyroid glands produce. Blood tests every six to 12 months to measure thyroid levels also are recommended.
Ms Fernandez is the latest South American leader to be diagnosed with cancer. Presidents Fernando Lugo of Paraguay, Hugo Chavez of Venezuela and Dilma Rousseff of Brazil have all undergone treatments recently.