BEVERLY When 16-year-old Erik West found out he has an extremely rare form of cancer, he wasn't scared, he said.

After all, his friend Mike Petrosino survived the exact same thing.

"I'm not worried," he said. "The night they told me, my mom ... Boston has some of the best doctors in the world."

Among them is Dr. David Ebb at Massachusetts General Hospital for Children. He took care of Petrosino, who was diagnosed three years ago, and now Mike is helping Erik as he goes through chemotherapy and radiation.

The two boys are juniors at Beverly High School. They were born days apart in June at Beverly Hospital. And they were both diagnosed with a rare cancer called Ewing's sarcoma, in the form of a malignant tumor that started in the same place on the right side of their pelvises.

"There's only 150 cases a year diagnosed in the U.S.," said Paula Petrosino, Mike's mother. "What are the odds of two kids in Beverly?"

"It's bizarre," said Elaine West, Erik's mother.

Indeed, the odds are low for two boys in the same city to be diagnosed with the same rare cancer, Ebb said.

"We were all sort of blown away by how strange and unlikely that was," he said.

While doctors can diagnose the cancer by identifying genetically rearranged chromosomes, they don't know what causes it. It would be jumping to conclusions to say the two cases are linked.

"Proving beyond a doubt there is some unifying environmental exposure is a tough thing to do," he said. It could just as easily be an unfortunate coincidence.

Despite the situation, Ebb said it's a great benefit for Erik to have Mike there to help him through what will be a long, tough treatment.

"Kids can really help each other out in a tremendous way," Ebb said. "Mike can offer the kind of support that nobody else can."

Erik finds comfort in talking to someone who's been through it.

"I try to be realistic," Mike said. "I don't lie."

Erik had his first chemotherapy treatment two weeks ago and goes in this week for a five-day intensive treatment.

"I didn't eat at all the five days I was there," Mike said. He lost about 30 pounds.

He told Erik to fatten up beforehand and warned him not to have anything spicy after the treatment.

With his blood count down and an increased risk of getting sick, Mike missed his freshman year of high school. He recommended the same tutor to Erik, who plans to take the rest of this year off and hopefully return for his senior year.

The two also just hang out, playing guitar and computer games.

"It's not so much what he says, but the fact he's sitting here," Erik said.

Both boys were wearing rubber yellow cancer support bracelets, which friends at Beverly High School plan to start selling as a fundraiser for Erik.

"I plan on wearing it and not taking it off," he said.

He's also started reading the Bible.

"He's turning to it now, as much as he didn't want to go to church with me on Sundays," Elaine said, teasing him.

"It's just faith," Erik said.

The two boys were both healthy growing up. But in October, Erik was lifting dishes at the City Side Diner and hurt his back.

"It just persisted, and the pain got worse," he said.

He got physical therapy and then doctors X-rayed his back and found some narrowing of the spine.

Thinking it might be rheumatoid arthritis, they ordered more tests.

The fevers started two days after Christmas, with temperatures spiking to 104 degrees, and doctors pinpointed the tumor in his pelvic region. It's spread up his spine, to his lungs, and the back of his head.

Nearly three years ago, Mike had similar symptoms over the 2006 April vacation.

"We thought it was the flu," Paula Petrosino said. When he was diagnosed, the cancer had spread to about the same regions as in Erik.

"And they told us they caught it early," she said.

Sitting on the couch at Erik's, the two boys whispered to each other as their mothers discussed the chances of this happening to two friends with so much in common.

"You can't point fingers," Paula said. "You can't say, 'I think it's this.'"

But it makes them wonder, where did the boys go when they were younger? Where did they play?

Is there something in the dirt in their backyards? Something in school? Something in the hospital during that first week of June 1992?

"I want somebody to look into something," Paula Petrosino said. "I want it investigated."

"We've got a long road ahead of us," Elaine said.