Barcelona coach Tito Vilanova will have surgery on his parotid gland tomorrow before undergoing six weeks of chemotherapy, the club have confirmed.
He had an operation on a tumour in his saliva glands in November 2011.
Vilanova took over as Barca coach from Guardiola at the end of last season and presided over a seamless transition, guiding them to a nine-point lead at the top of La Liga after 16 games.
Reports in the Spanish press suggest Vilanova is likely to leave the Camp Nou.
Tens of thousands of people are out on the streets of Barcelona protesting against the austerity cuts.
There are lots of families, students and union members. Plenty of firecrackers are going off but everything appears peaceful.
Celtic players Tony Watt and Fraser Forster have spoken of their joy after their team beat Barcelona in the Champions League.
It'll take a couple of hours to sink in. I just saw (Victor) Valdes, I thought to put it to the side of him and it might go in. It's probably the best moment of my life, I'll look back at it when I'm older and think 'We've just beaten Barcelona in the Champions League' - there's nothing better.
It's tremendous, I don't think words can describe it. We put in so much effort at the Nou Camp and couldn't see it through, and tonight we've seen it through. We had a good look two weeks ago and we knew what we wanted to do. Everyone was tremendous, everyone played their part tonight. We defended really well and Tony came on and scored a great goal; his goals-to-games ratio is incredible.
Goals from Victor Wanyama and Tony Watt have given Celtic a famous 2-1 home win against Barcelona.
Lionel Messi scored a consolation goal for the Spanish side in injury time.
Reuters is reporting that Tito Vilanova has agreed a two-year deal to succeed Pep Guardiola as coach of the Spanish club Barcelona.
Barcelona president Sandro Rosell has confirmed that manager Pep Guardiola will step down at the end of the season.
Pep Guardiola will quit Barcelona at the end of the season, according to Reuters.
Barcelona manager Pep Guardiola will hold a press conference at noon (BST) today to announce whether he will resign from the Spanish team.