Apple chief Steve Jobs today marked his formal return to the stage since returning to work from a nearly six-month medical leave, presenting at his company's special "Rock & Roll" music event. The executive didn't provide many details of the liver transplant that is already known to have triggered the leave but did mention that the transplant, which took place five months ago, gave him the liver of a person who had died in a car crash.

It's believed that the transplant stemmed from Jobs' previously cured pancreatic cancer having metastasized in his liver, a common event for those who suffer but are successfully treated for the cancer Jobs had years earlier. The presence of the cancer produced the "hormonal imbalance" Apple cited when Jobs first went on leave in January and is widely blamed for the rapid weight loss evident in Jobs' late 2008 keynotes.