While people with more than 50 moles may be at higher risk of developing melanoma, people who have fewer moles may be at greater risk of developing more aggressive melanoma.

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Having a large number of moles is a known risk factor for melanoma, the deadliest form of skin cancer.

This is the conclusion of new research presented at the American Academy of Dermatology’s 2015 Summer Academy Meeting in New York, NY.

Dr. Caroline C. Kim, a dermatologist from the Harvard Medical School in Boston, MA, explains that melanomas are not all the same genetically, and so there may be different pathways that drive melanoma in these two different patient groups.

While people with large numbers of moles may be more aware of their skin cancer risk than others, the research suggests that people with fewer moles may face a different kind of risk.

“If patients with fewer moles are more prone to aggressive melanoma, then we need to make sure that they are also being educated and screened, in addition to patients with many moles,” Dr. Kim adds.

Melanoma is the deadliest form of skin cancer. Although it accounts for less than 2% of skin cancer cases in the US, it causes a large majority of skin cancer deaths. According to the American Cancer Society, around 73,870 new melanomas will be diagnosed in 2015, and 9,940 people are expected to die from this form of cancer.

Having observed that patients with fewer moles appeared to develop more aggressive melanoma than patients with large numbers of moles, Dr. Kim and her colleagues decided to review the cases of 281 melanoma patients who had visited the Beth Israel Deaconess Medical Center Department of Dermatology at Harvard Medical School.

Of these patients, 89 had more than 50 moles, while the remaining patients had fewer than 50 moles.

Those who had fewer moles were often found to have thicker, more aggressive melanoma than the patients who had a large number of moles. Thinner, less aggressive moles tended to develop in patients who had both a high number of moles and atypical moles – both risk factors for melanoma.

Fast facts about melanoma
  • Melanoma occurs when pigment cells known as melanocytes become cancerous
  • Repeated overexposure to the sun is the only avoidable major cause of melanoma
  • Removing skin cancer tumors at an early enough stage is curative.

Learn more about melanoma

The researchers also noted that patients with 50 or more moles were more likely to be diagnosed with melanoma at an earlier age than the patients with fewer moles.

In addition to the potential biological explanation for these findings, Dr. Kim suggests that patients with a large number of moles may be more readily identified as being at risk for melanoma, leading to their melanoma being detected at an earlier stage due to better education and more frequent skin examination.

As this research was merely an observational study, Dr. Kim says that further large-scale studies are needed to validate the findings. Investigations into the biology of the melanoma of the two different patient groups are also necessitated, as is research on the benefits of population-wide skin cancer screenings.

“It’s important to educate yourself about skin cancer, no matter how many moles you have,” Dr. Kim concludes. “All skin cancers, including melanoma, are most treatable when they’re detected early, so it’s important to be aware of warning signs on your skin.”

The American Academy of Dermatology recommend regular self-examination for signs of suspicious spots on the skin. In particular, they state that individuals should look out for moles that are asymmetrical, have irregular borders, inconsistent coloring, change size over time and have a diameter larger than 6 millimeters.

Recently, Medical News Today reported on a study that found patients who undergo an organ transplant are at greater risk of developing melanoma compared with individuals who do not have a transplant.