TIMELINE: Key dates in health saga of Apple's Jobs

(Reuters) - Apple Inc Co-founder and Chief Executive Steve Jobs is back at work, returning from a near six-month medical leave after receiving a liver transplant.

Here is a timeline of his health issues:

August 2004: Jobs announces he underwent successful surgery to remove a cancerous tumor from his pancreas. He said it was a rare form of pancreatic cancer called an islet cell neuroendocrine tumor.

June 2005: Jobs mentions the cancer in a commencement address at Stanford University.

"This was the closest I've been to facing death, and I hope it's the closest I get for a few more decades," he says.

2008:

June 9: Jobs appears dramatically thinner at an Apple iPhone event, touching off speculation the cancer had returned. The company said he was fighting a "common bug" and taking antibiotics. Apple later called Jobs' health a "private matter."

July 26: The New York Times journalist Joe Nocera wrote in a column that he had spoken to Jobs about his health but that because the conversation was off record, he could not disclose what was said. "While his health problems amounted to a good deal more than 'a common bug,' they weren't life-threatening and he doesn't have a recurrence of cancer," Nocera wrote.

September 9: At an iPod product launch, Jobs jokes about his health by walking on stage in front of a giant screen that flashed "The reports of my death are greatly exaggerated" -- a quotation borrowed from Mark Twain.

October 3: A false Internet report that Jobs had suffered a heart attack briefly pushes Apple shares down 2 percent to a 17-month low. Apple quickly denied the report on iReport.com, a citizen journalist site owned by CNN.

October 14: At a Mac product launch event, Jobs jokes again about his health. His blood pressure was 110 over 70 and he said, "And that's all we're going to be talking about Steve's health today."

December 16: Apple said Jobs won't deliver the keynote address at the Macworld trade show in January, reviving concerns about his health. Asked to explain the decision, a spokesman said it would be the last time Apple takes part in Macworld so "it doesn't make sense for us to make a major investment in a trade show we'll no longer be attending."

December 30: Apple shares fall as much as 2 percent after Gizmodo reported that Jobs health was "rapidly declining" and that was the reason why he canceled the Macworld keynote.

2009:

January 5: Jobs says he has been losing weight throughout 2008 and his doctors think a hormone imbalance was "robbing" him of proteins. He says he has begun a "relatively simple and straightforward" treatment for his nutritional problem and that he will continue as CEO during recovery.

"I will be the first one to step up and tell our board of directors if I can no longer continue to fulfill my duties as Apple's CEO," he says. Apple shares rise 5 percent.