Once again, Apple Inc Chief Executive Steve Jobs is taking medical leave — the third time since 2004 — and once again, the company's stock price is plunging as Jobs declines to share details about his condition.
Whatever is forcing Jobs to take time off, it is likely linked to a rare form of cancer called a pancreatic islet cell neuroendocrine tumor.
Although the cancer is broadly lumped in with pancreatic cancer, neuroendocrine tumors have a different nature from most pancreatic tumors, which are highly lethal and which kill 95 percent of patients within five years.
Pancreatic cancer is diagnosed in nearly 37,000 people a year in the United States and kills more than 34,000, according to the American Cancer Society.
But most of these cases are a type of tumor called adenocarcinoma. Neuroendocrine tumors are more easily treated and less aggressive. According to the National Cancer Institute, there are only 200 to 1,000 new cases a year.
Jobs had a neuroendocrine tumor removed in 2004 and said afterwards all the cancer was gone, and he did not require chemotherapy or radiation treatment.
Chemo or radiation is used to kill off any stray tumor cells that could spread and take up residence elsewhere in the body, seeding a new tumor.
Jobs remained noticeably thin, even gaunt, however, and took time off in 2009 to deal with what he termed a hormone imbalance, again giving few details.
Hormone effects can be caused by neuroendocrine tumors.
There are at least five different sub-types of neuroendocrine tumors, and one, called a glucagonoma, affects the hormone glucagon which in turn helps the body handle glucose.
One of the many symptoms these tumors can cause is unexplained weight loss, as well as a skin rash. Two other types of neuroendocrine tumors, one called a VIPoma and another called a somatostatinomas, can also cause weight loss.
These tumors may spread to the liver, and an experimental treatment is a liver transplant. Jobs had a liver transplant in 2009 but never said if it was related to his cancer.
According to the University of California San Francisco, as many as 80 percent of patients who get liver transplants to treat this kind of cancer live for at least five years.
Much depends on how badly the liver is affected.
Some experts said Jobs most likely got the liver transplant because the tumor had spread but Jobs has never given these details.
Liver transplants themselves carry complications.
In December, a team of experts from Germany and Greece reviewed 20 studies involving 89 patients who got liver transplants to treat pancreatic neuroendocrine tumors.
They found that 44 percent of the patients were alive five years later. Much depended on the age of the patient — Jobs at 55 just makes the cutoff — and which particular subtype of tumor they originally had, the researchers reported in the journal Transplantation.
Those with VIPomas fared the best, they said.
But any reporting on Jobs's health is speculative unless he allows more details of his condition to be released.