Argentine President Cristina Fernandez will undergo surgery on Jan. 4 to remove a tumor on her thyroid gland, presidential spokesman Alfredo Scoccimarro said.

The tumor was discovered when the 58-year-old president underwent a routine medical exam, Scoccimarro said.

Fernandez’s other organs have not been affected by the tumor, the presidential spokesman said.

After the operation, the president plans to take sick leave until Jan. 24, Scoccimarro said.