Having more than 11 moles on one arm indicates a higher than average risk of skin cancer or melanoma, research suggests. Melanoma is a type of skin cancer affecting more than 13,000 in the UK each year. It develops from abnormal moles, so the risk of being diagnosed with melanoma is linked to the number of moles a patient has. Researchers from King’s college London came up with this quick and easy way to assess the risk of skin cancer after series of test over a period of eight years. A mole is a small dark raised mark on the skin.