"He's a very young man, 36 years of age".
Miller made his professional debut for Celtic in 2000 after coming through the youth ranks at Parkhead and helped them win the Scottish Premier League title in 2004.
Fellow Corkman David Meyler added: "We heard the news but we were unsure of all the details".
Miller has played for both Martin O'Neill and Roy Keane, and was signed by Alex Ferguson, during a club career that began with Celtic where the current Ireland boss handed him his first team debut in the 2003-04 season. All thoughts go out to him and his family, I think he has three children as well.More news: The Ashes: Ryan Harris believes Australia will exploit England's "vulnerable" batting
The former Welsh worldwide said: "My thoughts are with Liam Miller and his family this morning".
The news was revealed by his former Hibs colleague Tam McManus, who also said Miller is due to start chemotherapy.
"The thoughts of everyone at Manchester United go out to Liam Miller and his loved ones at this hard time", read a post from the club's official Twitter account.
He tweeted: "Awful news about Liam Miller keep fingers crossed that he somehow pulls through".
Miller moved to Australia in 2011 to join Perth Glory, but is now contracted to semi-professional American club Wilmington Hammerheads FC.