It is a rare type of cancer called pancreatic neuroendocrine tumor that afflicts the hormone producing islet cells in the pancreas.

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"The two different types have fairly dramatically different clinical behaviors, " said Matthew Kulke, director of the carcinoid and pancreatic neuroendocrine tumor program at the Harvard-affiliated Dana-Farber Cancer Institute in Boston.

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But Mr. Jobs had what is called a neuroendocrine pancreatic tumor, a type that accounts for fewer than 5% of pancreatic cancers and, experts say, differs substantially from the more common kind.

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Statistics for pancreatic neuroendocrine tumors, a rare tumor type that is not as aggressive as standard pancreatic cancer, are murkier and less reliable given how few patients there are.

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In an unusual move, it plans to test Afinitor simultaneously on five other tumor types, including stomach, breast and neuroendocrine tumors (the type Apple's Steve Jobs has suffered from).

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