SAN FRANCISCO (Reuters) - Microsoft Corp co-founder Paul Allen has been diagnosed with non-Hodgkin’s lymphoma and has begun treatment, a spokesman for his investment company said on Monday.

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Employees of Vulcan Inc, which Allen formed in 1986 to manage his business dealings and philanthropic activity, were informed of Allen’s illness in a company e-mail on Monday.

“He’s feeling pretty good, he’s remaining very active at Vulcan and his other holdings and interests and he has no plans to cut back on any of that,” said Vulcan spokesman David Postman.

Postman said Allen’s diagnosis was recent and that treatment has already begun.

Allen, the 32nd richest person in the world according to Forbes magazine, co-founded Microsoft in 1975 with Bill Gates and resigned as an executive in 1983. He was diagnosed with Hodgkin’s disease in 1983 but his cancer was successfully treated.

Non-Hodgkin’s lymphoma is a type of cancer that originates in the lymphatic system, which is the body’s disease-fighting network. It is a far more common disease than the related but distinct Hodgkin’s.

In 2009 there were nearly 66,000 new cases of non-Hodgkin’s lymphoma and 19,500 deaths, according to the National Cancer Institute.

Through Vulcan, Allen has been a high-profile investor in his home town of Seattle.

He owns the Seattle Seahawks American football team and is a minority owner of the Seattle Sounders soccer team. He created the Experience Music Project pop museum in the city and is leading the development of a run-down area near Seattle’s Lake Union into a center for biotech research.

Allen is also chairman of cable company Charter Communications Inc.