The 36-year-old, who played with Celtic and Manchester United as well as a season with Cork City in 2015, is home in Cork to undergo treatment for the illness.
In recent seasons, he has been playing with Wilmington Hammerheads in the United States, where he lives with his wife and family. It is understood he had been treated there in recent weeks before making the decision to return home. His parents live in the family home in Ovens.
Pat Malone, chairman of Éire Óg where Liam played as a child, said the whole community was rallying in support of the family.
“There is a lot of shock in the community,” he said. “The family would be very well known in the area, they have lived here all their lives.
“He played with us and with soccer clubs in the area. Soccer was always his first love but at underage he played a lot with us, as did his brothers.”
A midfielder, Liam began his career with Celtic and spent two seasons with Manchester United as well as periods with Leeds United, Sunderland and QPR. He also played at international level from U19 up, earning 20 senior caps with the Republic of Ireland between 2004 and 2009.
Many former teammates have sent their good wishes to the midfielder.
John Hartson, who played with Liam at Celtic, said: “My thoughts are with Liam Miller and his family this morning. I hope he can get through this difficult time of his life.”
A number of former Ireland internationals have expressed their sorrow at news of his illness.
Fellow Ireland international Ian Harte said: “Very sad news about one of my old teammates Liam Miller, thinking of him and his family at this very difficult time.”
“Such sad news about my old roommate Liam Miller,” said former Leeds and Reading player Noel Hunt. “Pray to God he pulls through this battle with cancer, my thoughts and prayers are with him and his family.”
Former Celtic player Darren O’Dea added: “All my thoughts and love with Liam Miller and his family.”