Pele has revealed he last week underwent successful surgery to remove a tumor in his large intestine.
The Brazil legend, who won three World Cups, had previously taken to Instagram to deny claims he had fainted, posting he was "in very good health" after "routine exams".
However, Pele reportedly remained in hospital and on Monday explained why he had required medical attention.
"Last Saturday I underwent surgery to remove a suspicious lesion in the right colon," the 80-year-old wrote on his social media page.
"The tumor was identified during the tests I mentioned last week. Fortunately, I'm used to celebrating great victories alongside you.
"I will face this match with a smile on my face, a lot of optimism and joy for living surrounded by the love of my family and friends."