"Today we mourn our boss, mentor and friend whose 65 years were too short - and acknowledge the honour it has been to work alongside someone whose life transformed the world".
A successful treatment for non-Hodgkin's lymphoma led to Allen resigning from Microsoft in 1983, although at that time he retained his seat on the Microsoft board, eventually winding up as vice-chairman.
He stepped down as an officer of the company in 1983 because he was grappling with Hodgkin's lymphoma.
Allen had announced in early October that his cancer had returned after it had gone into remission in 2009. At 46th position, Paul Allen was estimated to have net worth of $20.2 billion. He was the 44-richest person in the world and the 21-richest person in America.
Gates and Allen became billionaires when Microsoft was thrust onto the throne of technology.
Aside from his fame as Microsoft co-founder and philanthropist, Paul Allen's life centred on a twin obsession with sport and the fate of warships sunk in critical battles during the war in the Pacific.
The Seahawks recently announced that Chuck Arnold would take over as president of the team, but sources indicated that was not related to Allen's illness. He's also the co-owner of the MLS' Seattle Sounders FC.
"A high-tech demigod" is how Sports Illustrated described the man who came up with the name for Microsoft, a company whose ubiquitous products include the Windows operating system and the Office suite of software.
Annual mammograms key to early breast cancer detection
A member of the public commented that these drugs would only "buy about two more years" for people with advanced breast cancer. When the NFL's Crucial Catch campaign was initially started, most of its focus was put on breast cancer awareness .
Some of his money went toward cutting-edge research.
Vulan Inc. was one of Allen's most recent ventures-a parent corporation that served as an umbrella for his holdings including his ownership in the Seattle Seahawks, the Allen Institute for Brain Science, and the Flying Heritage Collection.
Allen wrote that he had expected a 50-50 split in the new company, but Gates insisted on taking 60%, and later raised it to 64%, claiming that Gates schemed to "rip me off". Vulcan's investment arm, Vulcan Capital invested in companies such as Redfin, Flipkart, Spotify, Uber, TrueCar, and Waterpik. He established the Museum of Pop Culture in Seattle, along with a number of other institutions to showcase his collection of art, aircraft, computers, and memorabilia.
A nurse checks the temperature of a girl possibly infected with Ebola.
Paul donated more than $2 billion to various charities.
Gates said he was heartbroken about the loss of one of his "oldest and dearest friends".
"My brother was a remarkable individual on every level", his sister Jody Allen said in a statement. She continued: "Paul's family and friends were blessed to experience his wit, warmth, his generosity and deep concern".
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