The 18-year-old Gordon, a senior tri-captain on the powerhouse Hingham Harbormen, is scheduled to graduate on Saturday. He plans to be there. But it won’t be easy. For the past two months, Gordon has spent more time in doctors’ offices and hospitals than classes or hockey rinks. Shortly after the Harbormen fell to eventual champion Malden Catholic in the state’s Super 8 tournament, Gordon confided to his mother, Terry Gordon, that he was having pain in his groin area.

Within days, James Gordon was in an oncologist’s office. The diagnosis was knee-buckling. Gordon had Stage III metastatic testicular cancer. The most aggressive form of the cancer, the disease had entered Gordon’s abdomen and lungs.

“I slid down the wall and hit the floor in the doctor’s office,’’ said Terry Gordon. “I was in shock.’’

Gordon quickly underwent surgery to remove the cancerous testicle, and began four 21-day chemotherapy cycles. The first five days of each cycle are brutal, with successive chemo doses that leave Gordon exhausted, nauseated, and prone to headaches and bloody noses.

“He’s scared. We’re scared,’’ said Terry Gordon. “People say, ‘Oh, that’s a great picture of your son on the front page of the paper,’ and I say ‘He’s freaking bald.’ Yeah, he looks good, but it’s not something you want to see.’’

The news of Gordon’s condition spread quickly.

“I was devastated,’’ said Hingham High coach Tony Messina. “I could not believe it. Especially these high school kids. You think that they’re invincible.’’

So do many of the players themselves. “An 18-year-old kid? You never see that coming,’’ said Jim Gordon, James’s father. “When I went into Dana Farber with him, those other chairs are filled with kids, and I was just floored. Cancer is a disease that has no boundaries.’’

Information is key

Another core principle for an athlete—“know and respect your opponent’’—is also crucial in battling this kind of cancer. According to the American Cancer Society, testicular cancer is the most prevalent form of cancer in men ages 18 to 35. But getting young men to realize something could be wrong is challenging.

“It’s not even on their thought list that they’re anything but invincible, and they don’t think they have cancer,’’ said Dr. Douglas Dahl, chief of urologic oncology at Massachusetts General Hospital, of his teenage patients. “Plus, it’s a sensitive, awkward thing. They’re still children.’’

Early detection is paramount. Gordon acknowledged something didn’t feel quite right as long as nine months ago, but dismissed a size discrepancy because he wasn’t in pain. Hockey was his focus, and his play didn’t provide any indication that he was sick.

“I just put it in the back of my mind,’’ said Gordon. “I didn’t think about it, because I had a bunch of stuff going on, with hockey, and it didn’t really bother me.’’

However, one of testicular cancer’s most insidious characteristics, said Dahl, is that early stages are rarely painful. Gordon was in the midst of an MVP-caliber season—the Globe All-Scholastic would tally 21 goals and 19 assists to lead the Harbormen in scoring—that gave no hint that anything was wrong.

“I wish he would have noticed this, or he would have come to us sooner, but he’s a kid,’’ said Jim Gordon. “He thought it was a strain or something. He didn’t think it was cancer. Nobody does. But he did not want to sit. He just wanted to play hockey, and he fought right through it.’’

Strong faith

James is the oldest of four Gordon children. The youngest, 2-year-old Jennavive, has Down syndrome. But, according to Messina, the Gordons have a strong faith, and a strong support network.

“We don’t get to choose who gets sick and who doesn’t,’’ said Terry Gordon.

Shortly after Gordon’s diagnosis, the family learned that the ethic of “team first’’ extends far beyond the inner circle of the young men who play for the Harbormen. The town, including the Gordons’ parish at the Church of the Resurrection, rallied around the family.

“Probably 24 hours after his diagnosis, there were meals for the next three months lined up,’’ said Ryan Linehan, one of Gordon’s close friends and another Hingham tri-captain.