While imagining Apple without Steve Jobs may be hard for some, his current health condition seems harder.

The former Apple CEO has been known to be very private about his health; neither he nor his company has publicized concrete details of his condition. What is clear from reports however is that he has pancreatic cancer, a rare one.

Jobs suffers from pancreatic neuroendocrine tumor, which represents only 5% of all pancreatic cancers diagnosed each year. Like other pancreatic cancers, it is often found late and is hard to treat.

In fact, it doesn’t show symptoms right away. Symptoms are often vague or may go unnoticed. These include yellowing of the skin and eyes, pain in the abdomen and back, weight loss and fatigue. The pancreas is also gland behind the stomach and other organs, which can make it difficult for doctors to see or feel tumors during routine exams. (The pancreas helps controls sugar levels by producing digestive juices that aid in breaking down food and hormones.)

“People can coexist with the disease for years,” said Richard Goldberg, a neuroendocrine tumors expert at the University of North Carolina-Chapel Hill, who has not treated Jobs.

Though pancreatic cancer typically grows slowly, there comes a point when it speeds up, unless completely eradicated from the body. It can also spread to the liver, and if it fails, “people can go downhill pretty quickly,” added Goldberg. In the U.S., pancreatic cancer is the fourth-leading cause of cancer death.

While Apple proves to be in great shape, hopes are too for its most beloved former CEO. “I'm sorry to see him affected by this; it only redoubles my resolve to improve on the treatments we have,” said Goldberg.