Most moles and freckles are harmless – they make us unique.  Some moles or “freckles” occasionally change into pre-cancerous or cancerous lesions.  Patients with multiple moles that have unusual characteristics may have dysplastic nevus syndrome, a condition that has a high rate of conversion into melanoma.  Patients with excessive sun exposure may develop new skin changes that are actinic keratoses (scaly pre-cancerous lesions) or more serious squamous cell or basal cell cancers or melanomas.  Unfortunately, and in many cases, there is no substitute for an experienced dermatologist examination and biopsy to identify those patients at risk.