John Farnham's cancer tumour was in his mouth, wife reveals

The tumour that sent music legend John Farnham into a marathon surgery session was in his mouth, his wife Jill has revealed.

Farnham remains in a stable condition in intensive care this morning, after doctors operated from 8am-7.30pm yesterday.

The news of the 73-year-old singer's diagnosis came as a shock to Australia yesterday morning.

READ MORE: 'The Horses' singer dies at 57 after cancer battle

In a statement this morning, the Farnham family said they had been overwhelmed by the "incredible wave of support, love and messages" they had received.

"The cancer tumour was located in his mouth and it has been successfully removed," Jill Farnham said.

"There is still a long road of recovery and healing ahead of us, but we know John is up for that task."

The family also thanked the doctors, medical workers and surgical team that had been involved.

'He is the voice'

The diagnosis has prompted a wave of well wishes from around the world.

"I haven't spoke with him since his diagnosis but it was a big surprise for us as well for him," friend, Lindsay Field told 9News.

"He was here for lunch three weeks ago and it was lovely, there was no suspicion at that time of this.

"Anyone you love and care for, you have a concern for their well-being."

READ MORE: Teen about to set record as youngest person to fly solo around world

Molly Meldrum was among those wishing him the best in his operation and recovery.

"He has been a friend of mine for a very long time, and we have been through lots in that time," he told 9News.

"He is the voice, there is doubt about that and he will always be the voice.

Kiss founding member Paul Stanley also posted to social media in a show of support.

"John… You ARE the voice!!! We are all sending you our prayers, energy and light for a full recovery," Stanley tweeted.

READ MORE: Body of great white shark killed by 'serial' killer whales washes up

Earlier today, entertainment reporter Peter Ford told 3AW details about his specific illness remained unclear.

"We don't know too much about the type of cancer that he does have. We know there is a tumour involved, but we don't know where on his body that would be," he said.

The family has requested privacy during this time.

Farnham has been a mainstay of Australian entertainment since he was billed as teen idol "Johnny Farnham" in the late 1960s.

The 73-year-old's 1986 album Whispering Jack, featuring the single You're The Voice, remains the second-highest selling album in Australia, behind only Meat Loaf's Bat Out Of Hell (1977).

He has received 19 ARIA awards, and was named an Officer of the Order of Australia in 1996, and Australian of the Year in 1987.