Marshall requested that the type of cancer remain confidential.
Only a few of Marshall's close friends have known about the cancer, which was diagnosed about nine months ago.
"People are coming up with all this sympathy stuff, and I hate that," Marshall said. "I'm doing all right, I'm optimistic, and my life will continue."
Marshall will go to the Mayo Clinic in Rochester to consider options for treatment.
"I've got some options, and I plan on exercising those options," Marshall said. "There's chemotherapy and radiation treatments. It seems to have spread to the bone. Right now I'm in the process of choosing a method of treatment that might be available to me."
Marshall, 62, was one of the Purple People Eaters, the renowned defensive front that included Carl Eller, Alan Page and Gary Larsen under coach Bud Grant. He played in 270 consecutive games with the Vikings from 1961 to 1979.
He holds the NFL's record for consecutive games played, with 282 including his rookie season with the Cleveland Browns. He played in four Super Bowls and two Pro Bowls. The Vikings retired his No. 70 last year.
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