Chairman and Chief Executive of J.P. Morgan Chase & Co. Jamie Dimon told shareholders and employees Tuesday that he has been diagnosed with throat cancer. In a memo, Dimon wrote that the prognosis is "excellent" and he will be able to remain actively involved in the company.

Dimon, 58, made the announcement on his 10-year anniversary with J.P. Morgan, when he joined the group after merging with Bank One Corp. in 2004. He announced this discovery Tuesday as Dimon cancelled a planned five-country client trip.

In his memo to the bank board, Dimon explained that he will limit his travel while undergoing eight-week-long radiation and chemotherapy treatments. The cancer was caught quickly and is confined to one area, he stated.

Joe Evangelisti, a company spokesman, said that the CEO's responsibilities won't be shifted to any one individual while Dimon is in treatment. Individual business heads will continue as usual. According to Evangelisti, the biggest adjustment will be with Mr. Dimon's scheduled client visits.

Dimon plans to continue working through radiation and take an extended summer vacation while undergoing chemotherapy. The chairman will be given treatment at Memorial Sloan Kettering Cancer Center.

J.P. Morgan has seen a series of top executives leave in recent years. In the last two years, at least 10 senior executives have left. Michael Cavanaugh, considered a potential successor to Dimon, left most recently to join the private equity firm, the Carlyle Group.

While Dimon emphasized Tuesday that he would remain deeply involved in the day-to-day operations of the bank, more concern is raised about who would inherit the reigns should Dimon become too ill to run J.P. Morgan.

"The board had already established a short-term, medium-term and longer-term succession plan," Evangelisti said. Possible replacements include Gordon Smith, the company's consumer bank head, as well as Mary Erdoes, who leads the asset management business.