Warren Buffett announced in a letter to Berkshire Hathaway (BRKA) shareholders that he was diagnosed last week with stage I prostate cancer, a matter that's likely to renew speculation about his successor.

The 81-year-old Buffett, who serves as chairman and chief executive officer for the Omaha, Neb.-based company, said in the letter, released Tuesday after the market closed, that his “condition is not remotely life threatening or even debilitating in any meaningful way.”

Buffett said an array of other tests, including a CAT scan, bone scan and MRI have “showed no incidence of cancer elsewhere.” The famed Oracle of Omaha also disclosed that he feels “great -- as if I were in my normal excellent health -- and my energy level is 100%.”

Buffett will undergo a two-month stint of daily radiation treatment, beginning in July, which he said will disrupt his travel schedule but otherwise pose no change to his daily routine. He promised to inform shareholders immediately if his health should change.

“Of course, it will; but I believe that day is a long way off,” Buffett said.

Buffett disclosed in his annual letter to shareholders in February that the board had selected a candidate to take on the role of chief executive, when Buffett decides to step down from the post, but did not name that individual.  

Berkshire Hathaway class A shares slipped 1.32% in after-hours trading, after the stock finished the day up 1.5% at $121,310 a share.