Sad news out of the dog racing world ... 4-time Iditarod champion Lance Mackey passed away Wednesday after a battle with cancer. He was only 52.
As we previously reported, Mackey announced he was diagnosed with throat cancer for the 2nd time last August ... after beating the disease in 2001.
We're told the legendary dog musher was in and out of the hospital since June ... with Mackey saying on Facebook in August, "the past several months have been the hardest/worst part."
"Just wanted to say thanks to my friends and family for everything and I love you all so much.