Hall of Fame second baseman Ryne Sandberg, who played 15 seasons for the Chicago Cubs, announced on Instagram that he has been diagnosed with metastatic prostate cancer and has begun treatment.

"To my Chicago Cubs, National Baseball Hall of Fame, extended Baseball Family, the city of Chicago, and all my loyal fans, I want to share some personal news," Sandberg wrote in the post Monday. "Last week, I learned that I have been diagnosed with metastatic prostate cancer. I have begun treatment, and I am surrounded by my loving wife Margaret, our incredibly supportive family, the best medical care team, and our dear friends.

"We will continue to be positive, strong, and fight to beat this. Please keep us in your thoughts and prayers during this difficult time for me and my family."