BBC political editor Nick Robinson is being treated for a tumour but hopes to be back at work in time to cover the general election campaign, his agent said.
The 51-year-old journalist, who has led the corporation's Westminster coverage since 2005, needs an operation to remove a bronchial carcinoid tumour from his lung.
In a statement, his agent said Robinson, who is married with three children, would be "taking a short time off work over the next few weeks".
Robinson is possibly the most highly regarded political journalist in the UK
"His doctors are aiming to get him back at work in plenty of time to cover the election campaign proper," she added.
Thank you for the many kind and generous messages. Here's hoping to be back reporting the news soon
— Nick Robinson (@bbcnickrobinson) February 28, 2015
"He and his family have asked that they now have the space and privacy he needs in order to rest and recover fully before returning to work."
Carcinoid tumours are rare and tend to be slow growing, sometimes not causing any symptoms for several years, Cancer Research UK says on its website.
Around a quarter start in the lung and typically do not spread to other parts of the body.
A BBC spokesman said: "Everyone at the BBC wishes Nick a speedy recovery."
Prime Minister David Cameron was quick to offer his best wishes to the broadcaster.