A quarter of normal skin cells have cancer-associated mutations, researchers say. The study, published in Science, analyzed samples from middle-aged individuals and found 100 cancer-driving mutations in every 0.1 square inch of skin.
Researchers sequenced the genes from 234 biopsies, where a small sample of tissue is taken. These samples were taken from patients aged between 55 and 73 during routine surgery to remove excess skin from their eyelids. These mutations were mostly caused by exposure to sunlight.
Researchers found that the mutated cells formed clusters—called clones—that grew to be twice as big as normal ones. There’s no need to freak out, as researchers say none of these clones would have developed into tumors. The study does, however, provide researchers with an opportunity to analyze and break down the steps that result in a mutated cell in becoming cancerous.
“These first cancer-associated mutations give cells a boost compared to their normal neighbors. They have a burst of growth that increases the pool of cells waiting for the next mutation to push them even further. We can even see some cells in normal skin that have taken two or three such steps towards cancer. How many of these steps are needed to become fully cancerous? Maybe five, maybe 10, we don’t know yet,” says co-author Dr Peter Campbell, from the Wellcome Trust Sanger Institute, in a statement.
Skin cancer is one of the most common type of cancer in the world, accounting for one in three cancer diagnoses. Researchers linked the mutations they observed to the more common and treatable form of skin cancer called cutaneous squamous cell carcinoma, than the rarer form of skin cancer known as a melanoma.
“What we are seeing here are the hidden depths of the iceberg, not just the relatively small number that break through the surface waters to become cancer,” says Dr Iñigo Martincorena, first author from the Sanger Institute, in a statement.
Researchers hope to use the results from the study to gain a better understanding of the origin of skin cancer. Cancer Research UK’s health information manager, Sarah Williams, suggests that the findings of the study reinforces the importance of wearing sunscreen.
“Although we all need some sun, people can avoid sunburn and skin damage when the sun is strong by spending time in the shade, covering up with clothing and using plenty of sunscreen with at least SPF15 and 4 or more stars,” she explained in a statement.