A 21-year-old had the most dangerous form of skin cancer. It looked harmless, and she had no other symptoms.

Skin cancer can be difficult to spot and may not cause symptoms until later stages when the disease has spread. BSIP/UIG via Getty images A dermatologist shared the case study of a young patient with a mole that turned out to be skin cancer. Aggressive, dangerous skin cancers may be hard to spot, and don't always match typical warning signs. To reduce your risk, keep track of any new moles or marks, especially ones that change rapidly. A 21-year-old patient showed up at the dermatologist's ...