( CNN ) -- Microsoft co-founder Paul Allen has been diagnosed with non-Hodgkin 's lymphoma , more than 25 years after he was treated for Hodgkin 's disease , a spokesman at his company Vulcan Inc. told CNN on Monday . Allen , 56 , `` received the diagnosis early this month and has begun chemotherapy , '' Vulcan CEO Jody Allen said in a memo to Vulcan employees . The memo was posted Monday evening on CNET 's news site . `` Doctors say he has diffuse large B-cell lymphoma , a relatively common form of lymphoma , '' Jody Allen , who is Paul Allen 's sister , said in the memo . `` This is tough news for Paul and the family . But for those who know Paul 's story , you know he beat Hodgkin 's a little more than 25 years ago , and he is optimistic he can beat this , too . '' The memo said Paul Allen is feeling OK , is still working and `` has no plans to change his role at Vulcan , '' which is based in Seattle , Washington . Non-Hodgkin 's lymphoma , like the less-common Hodgkin 's disease , is a cancer of the lymphatic system . Hodgkin 's lymphoma is distinguished from the other by the presence of a certain type of cell . Allen , who co-founded Microsoft with Bill Gates in the mid-1970s , was that company 's chief technologist until he left the company in 1983 , the year he was treated for Hodgkin 's lymphoma , according to the Web site for his Paul G. Allen Family Foundations . In September , Allen ranked 17th in the Forbes 400 list of richest Americans . His net worth was $ 11.5 billion , according to Forbes magazine . Among Allen 's business interests are the professional sports teams he owns , the NFL 's Seattle Seahawks and the NBA 's Portland Trail Blazers . He also is part owner of Major League Soccer 's Seattle Sounders FC . CNN 's Katy Byron contributed to this report .
Allen diagnosed with non - Hodgkin 's lymphoma . Diagnosis comes more than 25 years after he was treated for Hodgkin 's disease . He has begun treatment and is optimistic he can beat it , he said in interview .