One of the Microsoft co-founders Paul Allen has been diagnosed with cancer.

According to CNN, in early November he was diagnosed with diffuse large B-cell lymphoma (relatively common form of lymphoma) and began chemotherapy.

“Paul is feeling OK and is optimistic he can beat disease. He is still working and has no plans to change his role at Vulcan,” Vulcan CEO Jody Allen, Paul’s sister stated.

“Paul Allen was beaten by Hodgkin's disease more than 25 years ago. He was forced to receive X-ray therapy and bone marrow transplantation”, the source reads.

In September, Allen was ranked 17th in the Forbes 400 list of richest Americans. His net worth was estimated $11.5 billion.