It was just a kick in the shin — up high by his knee. But 16-year-old Matt Zender’s seemingly minor injury revealed a completely different and more devastating diagnosis.

“We thought it was a bone bruise,” Matt’s dad Mark, a physician assistant at Mather Hospital in Port Jefferson, said of the June 1 injury. “After two weeks, it wasn’t getting any better, and it was still painful. On X-rays images, a big area of his bone looked moth-eaten, hollowed out by a tumor inside the bone.”

Today at Stony Brook University Hospital,  Matt, a junior honors student and fencing team captain at Sayville High School, is expected to receive his first chemotherapy treatment, the start of his fight against an aggressive form of  bone cancer in his right lower leg.

Mark Zender, 48, said his son will have a chemo port implanted in his chest, be admitted to the hospital and immediately receive the cancer medication. A surgeon will also perform another biopsy to determine if the cancer has spread.

The arduous journey that lies ahead for Matt includes 30 weeks of chemotherapy and limb preservation surgery to his lower leg. The Zender family, including Matt’s mom Sally and his fellow triplets Christopher and Katie, anxiously awaits the results of a leg MRI and the final reading of a PET-CT scan to determine what stage Matt’s cancer is in.

“If the cancer is localized, he has a 65-75 percent chance for five-year survival. If it has spread — and is found in his lungs, the rate drops to 20 percent,” Mark Zender said. “It is all very scary. I alternate between clinical detachment and crying.”

Fencing epee captain

This spring, Matt experienced one of the best moments of his life when he was voted epee captain of Sayville’s varsity fencing team.

“He couldn’t believe it. To be chosen by his peers was phenomenal,” Mark Zender said, adding that his son was one of the founding members of Sayville’s fencing program several years ago.

Matt’s fencing coach Jill Brown has set up a GoFundMe page “Make it Matter for Matt” to raise funds to offset the financial burden of Matt’s medical treatment.

“Please know what a beautiful person Matt is,” the GoFundMe page description reads. “He is funny, kind and caring, full of energy and good to everyone around him.”

Matt, the “middle triplet” because he “came out second,” his father said, is an extraordinarily busy teen. Aside from fencing, he plays tenor saxophone, sings in the jazz choir, and is a stage crew member at Sayville High School. He is also a longtime and dedicated member of Scouts BSA Troop 184 and is a second-degree Japanese jiu-jitsu black belt.

What’s more, Matt has a 99 average in school — two points higher than his “older” (by a minute) sister Katie, but lower than his “younger” (by a minute) brother Christopher’s 100-plus average, Mark Zender said.

“He’s the happy-go-lucky kid, the one who’s always helping everybody else out,” Mark Zender said.

Matt’s positive energy will serve him well in his fight against cancer, his father said. “It’s a terrible scenario, but he has a great attitude, and he’s young and otherwise healthy.”