Example basal cell carcinoma, least malignant most, common type, arises from stratum basale. Squamous cell carcinoma, arises from stratum spinosum, metastasizes to lymph nodes, early removal allows a good chance of cure. Malignant melanoma, most deadly of skin cancers, cancer of melanocytes, metastasizes rapidly to lymph and blood vessels, detection uses ABCD rule.