(CNN) -- Golf legend Seve Ballesteros has confirmed that he has a brain tumor.
Ballesteros announced his retirement from competitive golf at last year's British Open.
The 51-year-old Spaniard has been in Madrid's Le Paz hospital since collapsing last Monday and broke news of the diagnosis in a statement.
"I inform you that after an exhaustive check, that was realized at Hospital La Paz, a brain tumor has been detected," he said.
"Throughout my career I have been among the best at overcoming challenges on the golf course. Now I want to be the best confronting the hardest challenge of my life, with all my strength," Ballesteros said in a statement.
Five-time major winner Ballesteros will undergo a biopsy on Tuesday before the doctors decide how to proceed.
It was unknown whether the tumor was benign or malignant.
Since being admitted he has been undergoing tests and on Friday, a statement by the hospital revealed Ballesteros had suffered "a partial epileptic fit" but said he had left intensive care and was in "a stable condition."
The former Ryder Cup captain, who won a record 50 times on the European tour, won the British Open three times and the U.S. Masters twice before retiring last year after battling back problems.
Ballesteros was also admitted to a hospital last year, and doctors discovered an irregular heartbeat.
Fellow Spanish golfers Jose Maria Olazabal and Miguel Angel Jimenez reacted to the announcement by wishing Ballesteros a speedy recovery.
Ryder Cup partner Olazabal, who visited Ballesteros in hospital, said he was "confident" he would recover, adding: "While I'm rightly worried, I thought Seve seemed very well. We were talking for a good while. I wish him a speedy recovery."
Jimenez added: "Seve, we love you. We all hope you recover as soon as possible and we're waiting for you."
Get well messages to Ballesteros, who is acknowledged to have revolutionized European golf with his flamboyant play, have been pouring in from all over the world.
Former European Ryder Cup captain Tony Jacklin summed up the mood of his admirers.
"At his best Seve was the best and the man who did more for golf than anyone else in Europe," said former two-time major winner Jacklin.
"He was our Arnold Palmer and people just love to see him play."
Ballesteros burst to prominence by winning the 1979 British Open at Royal Lytham, famously being dubbed the "car park champion" after a miraculous recovery shot from among the vehicles at the Lancashire course.
Another highlight of Ballesteros' career was captaining Europe to Ryder Cup success over the United States at Valderrama in 1997, but he became frustrated at his inability to rediscover former playing glories due to crippling back problems.
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