Melbourne AFL great Jim Stynes is battling cancer and will take time out from his role as president of the club to fight the disease.

Stynes, 43, first discovered a lump in his back three weeks ago.

Tests showed the lump was cancerous and that the disease had spread to other parts of his body.

"I need to put all my energies into getting my body right and to heal," Stynes told a media conference on Thursday.

"I'm not stepping down from Melbourne but I will be taking a break - I will have to take the rest of the season off."

Flanked by his wife Sam, Demons chief executive Cameron Schwab and vice-president Don McLardy, Stynes said he would go into hospital as soon as possible to begin therapy.

McLardy will take over as acting president until the end of the season.

Irish-born Stynes came to Australia in the mid-1980s and went on to have a decorated VFL/AFL career.

He played 264 games with Melbourne and won the 1991 Brownlow Medal and is a member of the AFL Hall of Fame.

Stynes took over as Demons president 12 months ago when Paul Gardner stepped down.

He has also won great admiration for his work with the Reach Foundation - a youth charity he set up.

Stynes, who has two children, has been named Victorian of the Year and won an Order of Australia Medal for his work with the charity.

Speaking in Darwin, Victorian Premier John Brumby wished Stynes well.

"Jim is a favourite Melbourne son," said Brumby.

"He's an inspirational footballer ... in every way I think he's been a great leader, a great footballer and he's been a great advocate for young people at risk in our community."

AFL chief executive Andrew Demetriou said all those involved in the football industry were united in their wish to support Stynes in his battle against illness.

"Jim is one of the most respected people in football and across the community and the best wishes of the AFL and all football supporters go out to him, his wife Sam and his family at this time," said Demetriou.

"The tireless job Jim has done in transforming the Melbourne Football Club and bringing together the club's supporter base has been incredible and I know football fans from across all clubs will pledge their support for him.

"We wish Jim a speedy recovery from his illness."