VISALIA, Calif. (KFSN) -- These are the last few weeks that Marcos Carrillo will walk the campus of Redwood High School in Visalia.
The senior is gearing up for graduation day.
He started his high school career across town at El Diamante.
He played football as the team kicker his freshman and sophomore years.
Ahead of his junior year, he transferred to Redwood High.
Unable to play football because of transfer rules, he stayed busy with his family, hanging out with friends and sticking to school work.
Then the spring semester came along, and he felt a lump in his right armpit.
"At first, I thought I had just injured it because it just felt sore. But then, eventually, we went to the doctor because it wasn't going away," Marcos said.
Doctors diagnosed him with Anaplastic large cell lymphoma (ALCL).
It's a rare form of non-Hodgkin lymphoma, meaning white blood cells grow out of control.
"I celebrated my birthday, but then the weekend after, that's when I started treatment," Marcos said.
In March of last year, right after turning 17, he started chemotherapy.
He would go to the hospital for five-day stretches.
If he didn't get sick, he'd go home for 21 days before returning to do it all again.
His mom stayed with him most of the time, but his friends and family would often visit.
Then, in August, after six long months of treatment, he got to ring the bell signifying he was done with chemo.
Marcos finished his junior year through independent study.
He was officially declared cancer-free and went back to school in October of last year.
"Physically, I felt good enough to be back. Mentally, it was like 'How am I going to catch up with work and stuff?'" Marcos said.
Despite the school work stacked against him, Marcos worked hard and finished the fall semester with a 3.6 GPA.
His Ethnic Studies teacher, Jacob Huerta Jr, says initially, he didn't know Marcos was a cancer survivor.
"You never would've realized that unless someone would've shared it because he just doesn't seem -- he seems like a nice, healthy young man." Huerta said. "It's very inspirational that he wants to be here, that he's trying his best, his hardest."
Things have been looking up for Marcos since returning to school.
During spring break, he got to go on a trip to Washington, D.C. with other kids who were hospitalized at Valley Children's Hospital.
They saw the monuments and took part in activities just for them.
But on the flight home, new concerns sparked as Marcos felt a familiar soreness in his armpit.
"I didn't feel a lump or anything, but I felt the soreness and the next day is when I felt like a little lump," Marcos said.
He's recently undergone tests and doctors determined that his cancer has returned.
He says, regardless, he's focused on making sure he's able to graduate.
"I mean, I'm still trying my best to turn in all my stuff so I still have my stuff to graduate if I'm healthy enough to walk. If not, then at least I know myself that I did what I could."
Marcos says his main priority after graduation will be staying healthy. After that, he wants to go to trade school to become an electrician.
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