Actor, host and "Good Morning America" contributor Cameron Mathison revealed earlier this week that doctors found a 4.2 centimeter mass on his right kidney.

In a new interview with "GMA," Mathison spoke about his upcoming surgery and how this tumor could have been growing for 10 years or more inside his kidney.

The host said the mass "is consistent with renal cell carcinoma."

"I'm just standing there and thinking to myself, I know this is just one of those dreams," Mathison said about the moment he got the news from his doctor.

But it wasn't a dream and he also admits he didn't know "if this was a death sentence."

"I called my wife," he said of the first thing he did after getting the news. "First thing out of her mouth, which is amazing to me is, 'We got this, we're going to beat it.'"

The MRI results came after years of abdominal pain and doctor visits trying to figure out what was wrong. He now urges everyone to take control of their health.

After the tumor was discovered, doctors also told Mathison they believe the mass was growing inside his kidney for 10 years or possibly longer. Amazingly enough, the tumor hasn't spread.

"I don't drink, eat incredibly healthy, I eat a very low sugar, low carbohydrate diet typically," he explained. "Things that likely in our best guess have have helped it from spreading, and growing even quicker."

Mathison is set to have surgery Thursday to remove the mass.

"We might be taking a kidney outta your body," he says doctors told him, depending on the surgery results.

After the interview, Dr. Jennifer Ashton said in Mathison's case, "Always trust your body."

While insurance and costs might make it hard for a doctor to send you for an MRI or another test right away after your first visit, no one knows your body better than you.

"The key is making the diagnosis as early as possible," she added.