Doctors discovered the tumor when Callaway had surgery earlier this week to remove his gall bladder. They say the condition is manageable and Callaway is expected to return to work in two weeks.
'I hate to miss work for any reason, so I am grateful that my doctors have made it possible for me to get back to the office quickly,' Callaway said in a statement.
Callaway has said he plans to retire this year as chief executive officer of the company, which has seen record sales in the first quarter thanks primarily to its ERC II driver, which conforms to the Rules of Golf everywhere except North America.
Company spokesman Larry Dorman said that tests are ongoing, but doctors have not suggested a treatment that would be radical or debilitating.
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