Sumbu Kalambay was a world champion boxer. He was born April 10, 1956 in Zaire. As a young man, he moved to Italy, which is where he still resides. April 10 is the 100th day of the year in the Gregorian calendar (101st in leap years). ... 1956 (MCMLVI) was a leap year starting on Sunday of the Gregorian calendar. ...

Kalambay turned professional in 1980. In 1985, he won the Italian middleweight title. Two years later, he won the European middleweight title by beating Herol Graham, who was 38-0 and ranked #1 in the world.

In his next fight, Kalambay defeated Iran Barkley to win the vacant WBA world middleweight title. He made three successful title defenses, including an upset win over Mike McCallum, the undefeated former world junior middleweight champion. World Boxing Association (WBA) is a boxing organization that sanctions official matches, and awards the WBA world championship title, at the professional level. ... One of boxings greatest champions, Mike McCallum was from Kingston, Jamaica, but fought almost exclusively in the USA. He first became a world champion by defeating the granite-hard Sean Mannion in his own home town to win the light-middleweight title, but came to prominence by knocking out...

In 1989, he fought Michael Nunn, the undefeated IBF world middleweight champion. Surprisingly, Kalambay was knocked out in the first round with one punch. It was the only knock out loss of his career. Michael Nunn was an American boxer who became the middleweight champion of the world. ... The International Boxing Federation, or IBF, is one of many organizations which sanction world championship boxing bouts, alongside the WBA, WBC, WBO, and a dozen or so others. ...

In 1991, in an attempt to regain the WBA world middleweight title, Kalambay had a rematch with McCallum, which McCallum won by a split decision. Two years later, after losing to Chris Pyatt in a try for the WBO world middleweight title, Kalambay retired with a record of 57-6-1 (33 KOs). The World Boxing Organization (WBO) is one of the sanctioning organizations currently recognizing professional boxing world champions. ...