In a study published online by the Journal of the American Medical Association (JAMA), Dr. Berwick and her team from the University of New Mexico Cancer Center discovered that patients with multiple melanoma tumors have a better chance of survival than those with only one.

Melanoma is the most serious form of skin cancer, and according to the American Cancer Society, there will be 76,600 cases of it in the US in 2013. With 75% of cancer-related deaths attributed to melanoma each year, it’s no wonder Dr. Marianne Berwick decided to conduct a study on it. But what she found is quite surprising:

“First, we wanted to know if people with a single primary tumor were more likely to die from melanoma than people with multiple primary tumors. They’re not.

But, if you match the thickness of the tumor, people with multiple primary tumors survive better.”

The most important factor in whether a person survives or not, according to the study, has to do with tumor thickness. If a tumor grows into the inner layer of skin, surviving melanoma becomes less likely.

Patients with several primary tumors that were 4 mm or deeper were nearly three times more likely to die than patients whose tumors were only 1 mm. What’s surprising is that patients with only one primary tumor that was 4 mm or deeper were 13.6 times more likely to die than patients whose tumors were only 1 mm.

Though the expectation is the opposite, according to Dr. Berwick, because most people would think more tumors are worse than one, she says:

“It seems that those people with multiple melanoma have some sort of native immune factor that’s helping them. It’s keeping the melanoma in check.”

The study involved patients from Australia, Canada, Italy and the US – 3,372 patients had a single tumor and 1,206 had multiple ones.

Although total fatalities in the study for patients with both single and multiple tumors were similar, the results showed that in terms of patients with the thicker tumors, single tumors caused a higher fatality rate than multiple tumors.

In light of this discovery, Dr. Berwick advises the public to visit a dermatologist at the first sight of a blemish or mole that appears to be growing. Because merely looking at a tumor from the skin level isn’t enough to determine how thick it is, visiting a doctor is the best way to catch melanoma early.

Though the study has yielded surprising results, Dr. Berwick is very excited about the work she and her team are doing “because there has been no cure for people who have deep melanomas. We’re just at that point where we can start to make a difference and that’s very motivating.”