In this Oct. 14, 2008 file photo, Apple CEO Steve Jobs smiles during a product announcement at Apple... 
(AP)Apple's history of keeping information about Jobs' health under wraps is only fueling the speculation. The company waited until after Jobs underwent surgery in 2004 to treat a very rare form of pancreatic cancer — an islet cell neuroendocrine tumor — before alerting investors. That type of cancer is easily cured if diagnosed early, unlike the deadlier and more common adenocarcinoma.
And last summer, Cupertino, Calif.-based Apple insisted Jobs' weight loss was due to a common bug, even as The New York Times cited anonymous sources who said Jobs had undergone "a surgical procedure" to address the problem.
Apple spokesman Steve Dowling would not elaborate on Jobs' condition or what he discovered in the past week.
"They'll tell you the least they can tell you," longtime industry analyst Roger Kay of Endpoint Technology Associates said after Jobs' disclosure Wednesday. "They're trying to have it both ways, to protect their guy's privacy and feelings and at the same time somehow signal the market."
Apple's chief operating officer, Tim Cook, will take over Jobs' responsibilities while he is on leave, though Jobs said he plans to remain involved in major strategic decisions.
Cook is seen as one of Jobs' most likely successors, along with Apple's top marketing executive, Philip Schiller. American Technology Research analyst Brian Marshall — who last week predicted Jobs would step down this year — said Wednesday's announcement tips the bets in Cook's favor.
"The company has been soft-signaling to the Street for a while now that Steve Jobs is not going to be CEO forever," he said. "This will be sort of a trial period for Cook to be chief executive."
Cook, 48, lacks Jobs' charisma and showmanship, but is seen as a solid pick. He ran Apple for two months in 2004 when Jobs was recovering from his cancer surgery.
"Tim Cook is a very experienced and highly regarded chief operating officer," said Calyon Securities analyst Shebly Seyrafi. "He's qualified."
