NBA Hall of Famer Dikembe Mutombo, one of the best defenders in the league's history, is undergoing treatment for a brain tumor, the league announced Saturday (Oct 15). Mutombo, 56, hails from the Democratic Republic of Congo, and has been a global ambassador for the National Basketball Association for years. He played for several teams throughout his long career, including the Denver Nuggets, the Philadelphia 76ers, the Atlanta Hawks and the then New Jersey Nets.