Paul Allen, who has owned the Seahawks since 1996 and Trail Blazers since 1988, announced that his non-Hodgkins lymphoma has returned. USATSI

Seattle Seahawks and Portland Trail Blazers owner Paul Allen announced Monday that he is fighting non-Hodgkins lymphoma. Allen previously had the disease in 2009 and fought it off, but it has returned. 

Allen made the announcement via Twitter. 

"My team of doctors has begun treatment of the disease and I plan on fighting this aggressively," Allen wrote on his website. "A lot has happened in medicine since I overcame this disease in 2009. My doctors are optimistic that I will see good results from the latest therapies, as am I."

According to the National Cancer Institute, 2.1 percent of people contract non-Hodgkins lymphoma at some point during their lives. Allen, who is 65 years old, is in the typical age range for when most people contract the disease (65 to 75 years old). Allen also fought off Hodgkin's lymphoma -- which is distinguished from non-Hodgkin's by the presence of certain cell types -- in 1982. Each are cancers of the lymphatic system. 

Allen, who co-founded Microsoft with Bill Gates, has owned the Trail Blazers since 1988 and the Seahawks since 1996. His company, Vulcan Sports & Entertainment, is also part of the ownership group for the Seattle Sounders of the MLS.