The Toronto Maple Leafs forward sent his friend, who has battled acute-lymphoblastic leukemia for more than four years, a signed personalized canvas and a special birthday wish on Twitter.

Tweet from @Marner93: Hi Hayden hope you had a great birthday! I was thinking of you Friday while getting ready for the outdoor game. You're a strong, brave girl & I'm proud to have you as my friend. Keep fighting & smiling, I'm rooting for you & can't wait to see you again #goteamhayden @lindsay0919 pic.twitter.com/5WZu0I7YXe

Tweet from @lindsay0919: What an amazing birthday surprise Hayden received today from the amazing @Marner93 !!! Thank you SO much Mitch! Hayden couldn���t believe her friend ���Mitch 1-6��� would send her a birthday present!! You made her feel special, and that���s all I ever want her to feel! #MapleLeafs #tml pic.twitter.com/OhmN1pHt6X

"When we saw that [Marner] had posted a message on Twitter, along with the picture, it made her feel so special," Hayden's mom, Lindsay Foulon, told NHL.com. "When the signed canvas arrived, calling her his friend, she grinned from ear to ear, and her smile melted my heart."

Hayden is from London, Ontario and has had cancer since she was 22 months old. She has gone through various treatments, including chemotherapy and stem-cell therapy, but the disease has relapsed twice. She is going through another round of chemotherapy at London Children's Hospital and will be off to Philadelphia for a new T-cell therapy treatment in the coming weeks in hopes of wiping out the cancer for good.

She first met Marner when he was a forward for London of the Ontario Hockey League, when he and then-teammate and current Arizona Coyotes forward Christian Dvorak stopped in to meet her at the hospital in 2015.

"Me and Dvorak used to go to hospital visits quite often, maybe once or twice a week every other week, and it was always nice to see the kids and put a smile on their face and they leave an impression on you as well," Marner told TSN last week. "She's been battling for her whole life, I just want to make sure she gets the support she needs and help that she needs and obviously that young fighting for that much stuff, it's amazing to see."

Hayden's family is made up mostly of Maple Leafs fans, except her father who cheers for the Detroit Red Wings, and when Marner started playing in Toronto last season, she began passionately following the team too.

"Eventually she would watch the games just to see Mitch and his No. 16 on the ice," Foulon said. "She would scream out 'There he is! Mitch 1-6!'"

Hayden has not been able to participate in daycare or traditional school because of her illness, which makes Marner's friendship all the more meaningful.

"He has been an important part of Hayden's cancer journey, and their friendship has been something to make her smile on days when she felt like doing anything but [smiling]," Foulon said. "So many kids look up to professional athletes as role models, and based on our experience with Mitch, Hayden couldn't have picked a better, more stand-up guy. He's got fans for life in our family."