He's undergone extensive rounds of chemotherapy and ultimately had part of his leg amputated in October.
For the past nine months, the Henriksen family has been traveling downstate for Grant's treatments. Grant's been bed-ridden for a lot of that time, recovering from various surgeries. But throughout it all, he's maintained a positive attitude.
"It's just something that I hope not a ton of people have to go through," says Grant.
"He really makes this so much easier for a parent to go through," says mom Tracy.
There are only 800 diagnosed cases of osteosarcoma a year. It's not hereditary and occurs mostly frequently in athletic boys, late in puberty.
Since being diagnosed with osteosarcoma, Grant's parents say he's only asked them for two things: a good prosthetic leg and the chance to ski here at home during the holiday season.
A born athlete who'd lost his natural balance and muscle mass, Grant says he initially struggled with skiing on just one leg.
"And I wanted to give up and just said do it next year when I'm stronger, but I decided to come back out another time and give it another shot, and I did a ton better," Grant says.
Grant's prognosis is good. His doctors say that the chemotherapy treatments have killed off about 95 percent of the cancerous tumor. Because of the aggressive nature of the type of cancer he has, Grant will continue receiving treatments until March.
Although his parents have experienced the ups and downs right along with their son, they say most of all, they're proud of his strength.
"It's exciting to see him out here. I watch people watch him, you know, when he's going across there on their lift and they're watching him. I know they're saying, 'Look at that one-legged kid skiing,' and it's like, hot dog yeah! Look at him, look at him go!"
And for all of the cards, letters, and phone calls he's received, Grant says:
"Thank you very much, it's just great to be in Marquette. It's just a great community, and people here are so nice and just, thank you."
To keep up with Grant's progress, you can visit his website by searching GHenriksen.
To see the full interview with Grant, click here .