The tumors could be primary lung cancers, meaning they originated in the lung. Or they could be growths that spread to her lung from cancer in another organ. The justice had colon cancer in 1999 and pancreatic cancer in 2009.

“When you have two lesions in the lung, it usually means it came from someplace else,” said Dr. Raja Flores, chairman of thoracic surgery at the Icahn School of Medicine at Mount Sinai in Manhattan. “It’s probably something that spread from the pancreas to the lungs.”

That Justice Ginsberg is alive 10 years after being treated for pancreatic cancer — which is often rapidly fatal — indicates that she probably had a relatively slow-growing form of the disease. Therefore, Dr. Flores said, he expected that the tumors in her lungs would also tend to be slow-growing, what he calls “turtles.”