Lou Brock, the Hall of Fame outfielder and former stolen-base king, has been diagnosed with a form of bone cancer, the St. Louis Cardinals announced Thursday.

Brock revealed that he's currently undergoing treatment for Multiple Myeloma, and as a result was forced to cancel a scheduled appearance at Busch Stadium later this month.

Due to cancer treatment, Lou Brock has canceled his appearance at the April 25 Busch Bash. Get well Lou! pic.twitter.com/6CNFt7f3zB — KSDK 5 On Your Side (@ksdknews) April 13, 2017

The 77-year-old Brock went through another major health scare in October 2015 when his leg had to be amputated due to complications from his diabetes. He recovered from that operation successfully, and was able to throw out the ceremonial first pitch at a Cardinals game last April.

Brock recorded 3,023 hits during his 19-year career with the Cardinals and Chicago Cubs, and retired as baseball's all-time stolen-base leader with 938. The Cardinals retired his No. 20 in 1979, and he was elected to the Hall of Fame in 1985.