Barcelona's France international Eric Abidal is to undergo surgery for a liver tumour, the club said on Tuesday.
The 31-year-old will undergo the operation on Friday at a Barcelona hospital, the Spanish champions announced in a brief statement on their website.
The club said: "A liver tumour has been detected in the player Eric Abidal and he will be treated surgically next Friday.
"Abidal will be operated on by Dr Josep Fuster Obregon. Per the express wish of the player, we call for the utmost respect for the right to privacy."
The central defender, who signed from Lyon in 2007, played in both legs of Barcelona's Champions League last 16 defeat of Arsenal.
Arsenal captain Cesc Fabregas reacted to the news on twitter, saying: "Much encouragement and a lot of strength to Eric Abidal. Bad news for football."
Real Madrid's Brazilian playmaker Kaka also wrote on twitter: "What sad news about Eric Abidal, tumor in the liver! Let's pray for him... God bless!!"
Abidal's Barcelona teammate, World Cup winner Andres Iniesta, offered his support on his Facebook page, saying: "I want to show all my affection and support for Eric Abidal. I'm sure everything will be okay."
Abidal has been capped 52 times for France, having made his debut for his country in 2004.
He has played in two World Cups, helping France reach the final in 2006, as well as Euro 2008.