Apple Chief Executive Steve Jobs underwent a liver transplant operation about two months ago and is expected to return to work by the end of June, The Wall Street Journal reported on Saturday.

Jobs, a pancreatic cancer survivor seen as the driving force behind development of the iPod, iPhone and other category-defining products from Apple's famed innovation machine, went on medical leave in January for an undisclosed condition.

A spokesman for Apple Inc would not confirm the Journal report but said, Steve continues to look forward to returning to Apple at the end of June and there is nothing further to say.

While investors may react negatively to the news on Monday, when stock markets re-open, analysts say Wall Street is broadly prepared for Jobs' shift to a role that sees him focusing on big pictures ideas and products at Apple.

Chief Operating Officer Tim Cook has been managing the company on a day-to-day basis in Jobs' absence, and is expected to continue to do so if Jobs does not return to the role full-time, analysts say.

The Journal, citing an unnamed source, said the 54-year-old Jobs may return to work part-time at first, with Cook taking on a more encompassing role.

The situation seems a lot more complex than it originally appeared, said Collins Stewart analyst Ashok Kumar. Investors tend to react negatively to uncertainty, especially when it concerns an individual who's had a larger-than-life impact.

Others said investors were aware of the risk surrounding Jobs and that it had been factored into Apple's share price.

The technology firm's stock fell after Jobs went on medical leave but is up around 60 percent this year, thanks to continued strong sales and new products, including the latest iPhone 3GS, which debuted on Friday.

Erick Maronak, chief investment officer for the Victory Large Cap Growth Fund, which owns Apple shares, said investors are less concerned than in the past because other executives had stepped to the forefront in Jobs' absence.

I think people are beginning to focus on core operations ... I don't think he's as important in terms of near-term volatility, Maronak said.

DISCLOSURE

Apple has been dogged for months by rumors about Jobs' health. In 2004, he was treated for a rare type of pancreatic cancer called an islet-cell, or neuroendocrine, tumor. These tumors usually grow slowly and are far less deadly than other types of pancreatic tumors.

Jobs' gaunt appearance at an Apple event in the summer of 2008 touched off speculation about his health, which was fueled by the crush of Apple blogs and fans that follow his every move.

In January, Jobs said his weight loss was due to a hormone imbalance and he would continue as CEO while being treated. Nine days later, he announced his medical leave, saying his health issues were more complex than previously thought.

Like many cancers, pancreatic cancer often spreads to the liver, compromising the vital organ's functioning, but it is not clear if Jobs may have received a transplant for that reason.

Some shareholders in the past have complained about Apple's lack of disclosure about Jobs' health.

At the same time, legal experts say there is usually no responsibility on a company's part to disclose a CEO's health status, and it is up to boards to decide how much to reveal to shareholders and the public.

Investors knew it was serious ... uncertainty about his health has been in the marketplace and has been affecting the stock for two years, said Patrick Coughlin, a trial lawyer at Coughlin Stoia Geller Rudman Robbins in San Diego.

Should they have been more candid? Probably, because he's so high-profile. I don't think they are in trouble from a shareholder-loss case standpoint.

The Journal said Jobs had the liver transplant in Tennessee and that at least some Apple directors were aware of the surgery.

Representatives for Methodist University Hospital in Memphis and Vanderbilt University Medical Center in Nashville said they did not perform the procedure on Jobs.

LIVER TRANSPLANTS

Liver transplants are becoming more common, with more than 6,000 performed in the United States in 2008, according to the United Network for Organ Sharing. Jobs' odds are good -- 70 percent of patients are alive three years after the procedure, UNOS said.

Across the nation 15,771 people are waiting for liver transplants, according to the U.S. Department of Health's Organ Procurement and Transplantation Network, and wait times vary by state.

UNOS said wait times had improved due to a new system that allocates livers based on need rather than time spent waiting.

Critical patients, for instance, may get a liver in just a few days, said Abhiunav Humar, head of the transplantation division at the University of Pittsburgh's medical center. There's no way of jumping ahead of the queue.

Humar, who has not treated Jobs, said he did not think a liver transplant would prevent him from leading Apple again. He has to take medication on a regular basis and have follow-up, but he should be able to lead a normal life.

(Reporting by Gabriel Madway in San Francisco, Maggie Fox and Roberta Rampton in Washington, and Gina Keating and Edwin Chan in Los Angeles; editing by Tiffany Wu and Paul Simao)

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