The legendary dog musher was first diagnosed with throat cancer back in 2001 -- and after surgery and radiation therapy, he was cancer-free.

But, Mackey announced on Tuesday via Facebook that the illness is back ... saying, "My winter plans just changed yet again."

"I was diagnosed with cancer again and being a single father has made sh* a bit different from my winter plans."

Mackey became an only parent when his partner, Jenne, died in a tragic ATV accident in October 2020 -- leaving him with their two children, Atigun and Lozen.

FYI, the Iditarod is the brutally difficult, 938-mile race that can last 2 weeks ... and Lance is one of the sport's best.

Despite not being able to race himself, Lance says he wants his pups to have a chance to compete.

"I’m not good about asking for help in any form — but here it goes. I have 8-10 dogs that deserve to race in a top team and 12 more that want to win — this season," Mackey says.

"All do respect to ALL,,,, not looking for sorry,,, just the right people for my dogs on a short term / winter deal ( unless is a team lease- sale )"

Mackey added, "I have every intention to race again, just won’t be this season!!!"

And, dog sled racing is in Mackey's blood ... his father is a musher and is one of the founders of the Iditarod Trail Sled Dog Race. His half-brother is also a musher.