A symptom is what you show. A cough is a symptom, detection of a viral protein is evidence of infection. I lost someone close to me to melanoma that metastasiz

A symptom is what you show. A cough is a symptom, detection of a viral protein is evidence of infection. I lost someone close to me to melanoma that metastasized to the brain. It grew for at least 6 months without symptoms. And when symptoms presented, they weren't immediately evident of a tumor until it had progressed. She was being actively monitored for melanoma at the time - having the ability to detect it earlier would have made all of the difference.