The cause of death was a blood clot.
Boytsov - nicknamed the “Russian Tyson” after American boxing legend Mike Tyson - won 36 of his 37 professional fights, 27 of them by knockout.
Boytsov challenged Wladimir Klitschko for the World Boxing Organization (WBO) world title in 2013. He fought his last fight in March 2015.
In May of that year, Boytsov was found unconscious in the Berlin subway.
He was placed in an induced coma and underwent surgery for severe head injuries. Boytsov never fully recovered and ended his boxing career.
The circumstances surrounding the incident have never been clarified.
