Status Quo guitarist Rick Parfitt is to undergo exploratory surgery after doctors found a growth on his larynx.
Parfitt had a quadruple heart bypass in 1997
The veteran rock band have called off the final dates of the UK tour, which will not be rescheduled.
Band manager Simon Porter said Parfitt had seen a consultant who "who expressed concern with a growth" and recommended urgent investigation.
The guitarist, who has been part of Status Quo for 40 years, had a quadruple bypass in 1997.
There has been speculation the growth in Parfitt's throat may be cancerous.
Mr Porter told the Daily Mirror they would not known the extent of the illness until next week "but we fear it is probably malignant".
Status Quo joined the cast of Coronation Street as guest stars
He is a smoker and has previously spoken of his early years with the band being filled with heavy drinking and drugs, although he says he has slowed down in recent years.
The decision to cancel the tour was taken after Parfitt was seen by doctors at Plymouth's Nuffield Hospital on Thursday.
Mr Porter said: "This morning Rick saw consultant Stephen Toynton, ENT surgeon at the Nuffield Hospital in Plymouth, who expressed concern with a growth in Rick's larynx and has recommended that it requires urgent investigation.
"Consequently all nine shows on the current sell-out UK tour have been cancelled.
"Whilst the band obviously regret having to disappoint their fans, they are thankful for their understanding at this difficult time and look forward to seeing them soon."
The veteran rockers are celebrating their 40th year as an act and recently released a DVD marking their four decades together.
Parfitt and his band partner Francis Rossi recently made two guest appearances on Coronation Street, playing themselves.
Status Quo have scored more hit singles than any other band in UK chart history, with 61 chart hits since their first smash, Pictures of Matchstick Men, was released in 1968.
Among their best-known songs are their British chart topper Down Down in 1974 and Rockin' All Over The World in 1977.