What are NMSCs? Non-melanoma skin cancers are the most common skin cancers. They arise from skin cells in the epidermis, the outer-most layer of the skin. The two most common NMSCs are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). BCC is the most common human cancer and accounts for 80% of all skin cancers. SCCs make up 16% of all skin cancers. BCCs and SCCs arise from keratinocytes, the cells that make up most of the epidermis.