Moles and melanomas both form from the same cell called melanocytes. Melanocytes are cells that give colour to the skin to protect it from the sun’s rays. It was thought that specific changes to the DNA sequence of melanocytes, called BRAF gene mutations, are what differentiates moles and melanomas: moles are usually harmless while melanocytes – with mutations in the BRAFV600E gene – are cancerous and often deadly without treatment.

However, research collaborators from the Huntsman Cancer Institute (HCI) and the University of California San Francisco, who studied moles and melanomas donated by patients using transcriptomic profiling (to determine molecular differences between moles and melanomas) and digital holographic cytometry (to track changes in human cells) found something new.

“We discovered a new molecular mechanism that explains how moles form, how melanomas form, and why moles sometimes become melanomas,” said Dr. Robert Judson-Torres, HCI researcher and University of Utah assistant professor of dermatology and oncological sciences.

The researchers found that melanocytes that turn into melanoma are affected by environmental signaling and do not need to have additional mutations. Environmental signalling is when cells receive signals from the environment in the skin around them that give them direction. Melanocytes express genes in different environments, telling them to either divide uncontrollably or stop dividing altogether.

These findings create a foundation for researching potential melanoma biomarkers, allowing doctors to detect cancerous changes in the blood at earlier stages. The researchers are also interested in using the data to better understand potential topical agents to reduce the risk of melanoma, delay development, or stop recurrence, and to detect melanoma early.

“Origins of melanoma being dependent on environmental signals gives a new outlook in prevention and treatment,” said Judson-Torres. “It plays a role in trying to combat melanoma by preventing and targeting genetic mutations. We might also be able to combat melanoma by changing the environment.”

“The current lifetime risk of an American developing invasive melanoma is 1 in 54 compared with 1 in 58 when we last reported in 2009,” a team of skin experts wrote.

According to Dr. Alex Glazer of the National Society for Cutaneous Medicine and his colleagues, more than 76,000 Americans would have been diagnosed with melanoma in 2016. More than 10,000 would have died from it, up from 8,500 in 2009, according to the American Cancer Society.

The incidence of melanoma has grown from 22.2 cases per 100,000 people to 23.6 cases per 100,000 people, they said.

“The overall burden of disease for melanoma is increasing and rising rates are not simply artifact owing to increased detection of indolent disease,” they wrote.

That’s still slower growth than in past decades. There was a 200% jump in deadly melanoma cases between 1973 and 2014. The American Cancer Society said that the rates of melanoma have been rising for the last 30 years.

Glazer and colleagues pointed to other studies that suggest more people are being diagnosed with melanoma because doctors are looking harder for it and getting better at detecting it.But they also noted that the mortality rate is rising faster than the detection rate, which suggests it’s not being caught earlier.