Paraguayan President Fernando Lugo has been diagnosed with a malignant tumour.
Doctors for Mr Lugo, 59, said the cancer, which appears to be in the early stages, was treatable with chemotherapy.
They discovered the lymphoma after carrying out a biopsy on a gland they had removed from Mr Lugo's groin during minor surgery on Wednesday.
Mr Lugo, a leftist former Catholic bishop, was elected two years ago, ending 61 years of conservative rule.
He served as a Roman Catholic bishop in one of Paraguay's poorest areas until stepping down in December 2006, saying he felt powerless to help the country's poor.
Mr Lugo shocked Paraguay last year when he admitted fathering a child while he was still a bishop.