Apple shares were off Thursday after photos emerged that purport to show an emaciated Steve Jobs entering a California cancer clinic for treatment.
Shares were down 1.28%, to $358.50, in pre-market trading.
RadarOnline and The National Enquirer reported that Jobs is receiving care at the Stanford Cancer Center in Palo Alto. The Enquirer published photos of a frail-looking Jobs entering the clinic. Two doctors who examined the photos for the tabloid but who have not personally treated the Apple CEO said Jobs' appearance indicates his condition is grave.
Apple has not commented on the reports.
Jobs on Jan. 17 announced that he would take "a medical leave of absence so I can focus on my health." It's his second health-related hiatus in as many years.
Jobs did not disclose details about his condition. Speculation has ranged from a return of the pancreatic cancer Jobs was first diagnosed with in 2003, or complications from a liver transplant he secretly underwent in 2008.
Jobs put chief operating officer Tim Cook in charge of day-to-day operations, but said that he would remain CEO and continue to be involved in major strategic decisions.
"I have great confidence in that Tim and the rest of the executive management team will do a terrific job executing the exciting plans we have in place for 2011," said Jobs. "I love Apple so much and hope to be back as soon as I can."
Some shareholders have criticized Apple for disclosing only scant information about Jobs' health, given his importance to the company. Others, including former SEC chairman Arthur Levitt, have said Apple's handling of the situation has been appropriate and that Jobs' health is a private matter.