Malignant Melanoma
Malignant melanoma is the least common of the major types of skin cancer but it can also be the most deadly. It can be caused by sun exposure but it can also arise in previously benign appearing moles. Years ago it was discovered that thicker the lesion, the more likely that it was to spread (metastasize) and the more deadly it could be. That is not an absolute rule but is usually accurate. The earlier that a melanoma is treated the less likely that is will cause any problems.