(CNN) -- Pancreatic cancer is rare and extraordinarily lethal, experts say.
Justice Ruth Bader Ginsburg's pancreatic cancer appears to have been found early.
Despite the relatively low number of people affected, about 95 percent of those with pancreatic cancer die from it, experts say.
"Of all the relatively common human cancers, it is by far has the highest death rate and worst outcome," said Dr. Andrew Lowy, chief of surgical oncology at the Moores University of California, San Diego Cancer Center. Justice Ruth Bader Ginsburg underwent surgery Thursday for apparent early-stage pancreatic cancer, the Supreme Court announced. Actor Patrick Swayze, Apple founder Steve Jobs and Carnegie Mellon University professor Randy Pausch, who died in July, also have publicly battled the disease.
Pancreatic cancer ranks as the fourth most common cause of cancer death in the country after lung, colon and breast cancer, according to the American Cancer Society.
The cancer is difficult to detect because of fairly general symptoms, such as abdominal pain, jaundice, loss of appetite, weight loss or depression. Sometimes, as in Ginsburg's case, there are no symptoms at all.
Ginsburg's small tumor was found in a CT scan during a routine annual check-up in late January, according to a statement from the Supreme Court. Ginsburg may have had the scan because of her prior battle against colorectal cancer, doctors say.
But using CT scans to detect pancreatic cancers are neither practical nor affordable, doctors say. Some of the existing tests are invasive or too sensitive and pick up changes that aren't associated with cancer.
While a mammogram is used to screen for breast cancer, colonoscopy for colon cancer and PAP smear for cervical cancer, there is no clear method for screening pancreatic cancer.
"For the average patient, it's one of those things with no good screening tests," said Lowy, a co-chairman of the National Cancer Institute's Pancreatic Cancer Task Force, which determines the direction of clinical research in the disease. "That's what makes it difficult. It doesn't produce early symptoms."
Progress has been made, but it doesn't compare with the ground gained against other forms of cancer, Lowy said.
"Screenings, all advances come through research," he said. "You don't luck into it. And research gets done when it's paid for."
Because cases of pancreatic cancer are uncommon compared with other cancers, funding is a major issue, Lowy said. Breast cancer, for example, represents about 200,000 new cases per year and about 40,000 deaths per year, while pancreatic cancer has about 38,000 new cases but about 36,000 deaths.
Many with pancreatic cancer find out too late. Even a small tumor in the pancreas tends to spread aggressively, doctors say.
"The chemotherapy is promising in colon cancer. It's not nearly as good for pancreatic cancer," said Dr. R. Matthew Walsh, a surgeon at the Cleveland Clinic.
One option is known as the Whipple procedure, in which the pancreas, part of the small intestine, bowel, stomach, biliary duct and gall bladder are removed. The removal of the pancreas leaves the patient with a lifetime dependency on insulin injections to metabolize sugar.
Smoking and obesity raise the risk of pancreatic cancer, according to Walsh.
Other risk factors include chronic pancreatitis and diabetes, said Dr. Otis W. Brawley, chief medical officer of the American Cancer Society and CNNhealth.com's condition expert.
Heredity, too, can play a role, Brawley said, noting that former President Jimmy Carter's mother, sister and brother all died of the disease.
For families with a history of pancreatic cancer, Lowy recommended finding out whether local universities have screening programs for the disease.
Research is under way to to find bio markers for the disease through a blood test that would detect a protein in pancreatic cancer patients that is missing in healthy patients. However, these efforts are "not close to being in the clinic," Lowy said.
CNN's Tom Watkins contributed to this report.