FitzSimons, in a memo to employees sent after his operation at the University of Chicago Medical Center, said tests indicate the disease is at an early stage. "Prospects are excellent for a quick and full recovery," he wrote, calling his medical situation "a slight detour."
In FitzSimons' absence, the company, which owns 11 major daily newspapers (including the Chicago Tribune and Los Angeles Times) along with two dozen television stations (including WGN-Ch. 9), will be managed by the eight other members of its corporate management team, according to the company.
That group includes Tribune Publishing President Scott Smith, Tribune Broadcasting President John Reardon and Tribune Interactive President Timothy Landon.
A source said FitzSimons, who turned 56 in June, expects to be released from the hospital Tuesday.
"Although I could think of more enjoyable ways to spend a summer vacation, I am fortunate to have great doctors and the support of family, our board of directors and colleagues," FitzSimons wrote.
FitzSimons, who in 2004 became the first chairman of Tribune to rise to the post through the company's broadcast ranks, has been embattled of late as Tribune, like so many traditional media companies, has seen its share price decline.
Tribune also has suffered from the fact its $8 billion Times Mirror acquisition in 2000 has failed to produce expected benefits while saddling Tribune with an inherited tax dispute that last year cost it $1 billion.
Before the announcement, Tribune shares were up 18 cents, closing regular trading Monday at $29.71. The stock is down 1.8 percent this year, having fallen 28 percent in 2005.
FitzSimons and a majority of the board earlier this year authorized a $2.5 billion repurchase of one-quarter of the company's outstanding shares.
That move was publicly opposed by the three board members representing the Chandler family, heirs to the Times Mirror fortune and, as a result of the buyback, now the company's largest shareholder.