The tumor was apparently found during routine testing that was part of an annual physical.
Ginsburg is a 10-year survivor of colon cancer. The cancers could be connected, but only in a minority of patients, Sasson said.
Ginsburg is not the first high-profile American to be stricken with pancreatic cancer in recent years.
Actor Patrick Swayze was diagnosed a year ago with pancreatic cancer. Meanwhile, speculation is rampant that Steve Jobs, CEO of Apple Inc., has had a recurrence of the less deadly form of the disease.
These high-profile cases don't indicate a rise in the incidence of the disease, which struck some 38,000 people in the United States in 2008, both Sasson and Ocean said.
The only known risk factors are smoking and a family history of the disease, Ocean said.
There are no specific screening protocols in place, which is why so many of these tumors are diagnosed so late.
"They're mostly diagnosed at a late stage because the symptoms don't happen until it's already late," Ocean said. "The symptoms can be very insidious, weight loss over time, vague abdominal pain."
Dr. Otis W. Brawley, chief medical officer of the American Cancer Society, said in a statement: "Justice Ginsburg's success in beating back a diagnosis of colon cancer nearly 10 years ago has inspired and given hope to many in the cancer fight. This new diagnosis is unfortunate, and we take hope in reports that this was apparently an early stage of disease, and wish her well, offer our support and prayers, and want to encourage her in what we know is going to be a challenging course of therapy."
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