February 4th, World Cancer Day at Signal Iduna Park in Dortmund, Germany: it's a day French-Ivorian striker Sébastien Haller will always remember.

Last summer, Haller was diagnosed with testicular cancer just weeks after signing a long-term contract to play for the second-biggest team in Germany, Borussia Dortmund.

It was a difficult, scary period for the big center forward when for the first time in his life, football was clearly not a priority.

But after two surgeries and four rounds of chemotherapy, the tumor was gone, and on World Cancer Day, he started his first game for the club.

"The thing you've been through, even if [you] don't really realize right now, you need to enjoy even more of your moments because this is something that you've missed for a couple of months," Haller told CNN.

Before the match and at half-time, Dortmund mascots came on the field to highlight International World Cancer Day by placing a model tumor in the center to raise awareness for testicular cancer.

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Dortmund were leading the visitors Freiburg 2-1, when in the 51st minute Haller scored a point-blank header off Raphaí«l Guerreiro's cross, capping off more than 4 months of hospital visits and physical therapy.

"You remember why you play football is [sic] truly that kind of moment, because scoring a goal, it's like I said, you feel like you are in the clouds," Haller told CNN Sport's Amanda Davies. "You feel like the atmosphere is changing."

WATCH the goal and the celebrations…

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