SANTIAGO, Chile (AP) — Uruguay’s former guerilla-turned-president, Jose Mujica, best known for transforming his tiny country into one of the most socially liberal in all of Latin America, said Monday that he has esophageal cancer.

Mujica, 88, said he was diagnosed during a routine medical checkup last Friday. He said the tumor discovered in his esophagus is particularly dangerous because he also suffers from an autoimmune disease.

“This is obviously very complicated and doubly so in my case,” the former president told reporters on Monday, adding that doctors were assessing the best course of action but told him chemotherapy and surgery posed challenges.

Better known as “Pepe” Mujica, the former president — once the leader of the Tupamaros, the Marxist urban guerrilla group that drew inspiration from the Cuban revolution — governed Uruguay from 2010 and 2015.